WHEN director Oliver Stone offered him the role of George W Bush in his controversial film W, Josh Brolin didn't need to think twice. He immediately turned him down.

"I couldn't understand it. I couldn't make any connection whatsoever. If anything, I was a little insulted," says the actor, sitting cross-legged in a crisp, dark business suit that smells faintly of the crafty illicit cigarette he's just smoked in his non-smoking hotel room.

"I wasn't mortally offended. I didn't say: 'Are you f***ing kidding me?' but I was certainly confused. But once Oliver came to me with the script and I finally sat down during a vacation with my family and read it from beginning to end, I learned that it was much more of a character study than a political smashing. Recently I had a dinner with another director who said to me: 'Don't forget that Oliver means it as a compliment.' I get that now."

Josh Brolin has played pig-headed types for most of his career, and when a stubborn actor meets an unconventional, obdurate director, you might confidently anticipate the clashing of alpha antlers. Instead, the two of them seem to have bonded and derive some glee from the puzzled response in some quarters to W. Stone's version of reality is kinder, however, than Michael Moore's Fahrenheit 9/11, turning George Bush's life into a hapless Oedipal parody.

"You disappoint me, Junior," says Bush senior, played by cinema's favourite patrician, James Cromwell. George has been in jail, in a bar hitting on a woman, getting his younger brother drunk, quitting his job in an oil field and generally failing his way through life, and his father hates the damage W has done to the family name: "Partying, chasing tail, driving drunk. What do you think you are – a Kennedy?"

At 40, Brolin easily agrees that he was at a perfect time in his life to grasp Bush, having been through failure and even disaster before arriving relatively late at success. He has seen hits and misses with quirky gems (Flirting With Disaster), third-lead flops (Hollow Man), lurches into television (Mister Sterling) and countless unseen flicks.

Married to actress Diane Lane, with two children, Trevor, 20, and Eden, 15, from his first marriage, there were times when Brolin only worked once a year. He even sold his ranch three years ago so he could continue the luxury of being selective, to the despair of his agent.

"Do I wish this success had happened earlier?" asks Brolin rhetorically. "Absolutely not, because I had kids very, very early on, so I got to be a dad and spend a lot of time with my kids. I may even have been happier then.

"People say: 'Oh, you must be so happy now that you've arrived. And in some ways I sort of feel like I arrived a long time ago. And in some ways I sort of feel like I never will. Before now I made enough money to live on; I didn't need the Mercedes or the yacht or the mansion. And even now we're still very modest how we live. So I like how things turned out."

Brolin is adamant that he has never been consumed by acting ambitions. "Maybe I flailed a little bit personally, although not in acting," he finally concedes. "I seem to go to jail a little too often. I told my kids recently – we have such good lives, we have exes that live a block either side of us, so we're all in it together. So I guess I just have to go to jail every so often, just karmically. I don't want to do anything bad, but it seems I keep coming to that."

As Brolin himself admits, he has a bit of a past. Police were called to his home on a domestic disturbance complaint four years ago. A spokesperson on behalf of Brolin and Diane Lane said it was a "misunderstanding".

Another of his brushes with the law was just three months ago while celebrating the end of the W shoot in Shreveport, Louisiana. Brolin, four crew members and Jeffrey Wright, who plays Colin Powell, the former US secretary of state, were arrested after an alleged bar brawl. Brolin's charge was interference with an arrest.

"There was no fight, there was no brawl," he says flatly. "There was a misunderstanding between Jeffrey and the bartender. The barman had a hard-on for Jeffrey; he was very rude and kicked him out of the bar and then the cops decided to come.

"I came out the bathroom as they were leading Jeffrey out and I decided to follow just to find out what was happening because there was no altercation. That turned out not so good. I was maced for I don't know why. To this day I don't know why. Can they do this sort of thing? They seem to feel that they can."

He's now resigned to the court case, which comes up on December 2.

For years, rather like Bush Jr, Josh Brolin lived in the shadow of his father James Brolin, television actor. In turn, James Brolin has, since 1998, become known as the husband of Barbra Streisand, although his son mischievously notes that their family was probably unique because "there wasn't a single Streisand album in the house".

"My dad was famous in TV when I was growing up, but as children we didn't grow up in Hollywood so we were removed from that fame.

"But he did give me a great disdain for acting while I was growing up because my dad was successful early on and the work took him away from us. We didn't live in LA and my mother kept us away from that side, so I didn't experience my dad's fame until I left home."

Josh Brolin is now famous in his own right since playing fortune-stealing cowboy Llewelyn Moss in the Oscar-winning No Country For Old Men earlier this year. "The Coen brothers turned my taped audition down and said I wasn't what they were looking for," he says cheerfully. "It was another month or so, after my agent had urged them to give me a reading, that I was able to meet them and read."

Before No Country For Old Men, his biggest role was as a teenager playing Brand, the workout fiend in the 1985 children's movie The Goonies. Steven Spielberg was the executive producer and frequently on set.

"I was reading Stanislavsky at the time," Brolin recalls. "One day we were in some caves, and I said: 'Maybe this is like Brand's mother's womb, and I could be scratching at the walls and crying.' Spielberg takes me aside and says: 'Man, just act. Just go out there and do it!'"

Twenty-three years later, Spielberg called Brolin after seeing No Country and told him they had to work together "now". Brolin says: "I was like, wow."

W paints the current president as a decent man who's too simple and too straight an arrow to cope with the devious schemers around him. To nail the accent, Brolin learned about 25 of Bush's speeches so that "instead of having to improvise, I had his words to say".

Brolin has great fun in the role: he has mastered the Bush accent and snicker, and the lightly fried approach to language, mispronouncing "nuclear", and "misunderestimating" the rhetorical traps that he randomly wanders into.

Early on, he's shown cramming food into his mouth and swilling beer, a man both under-used and over-endowed. After Bush loses a race for Congress, and has a born-again experience, Brolin suggests a man wheeling in search of a self. Yet as a card-carrying Democrat who even attended the convention where Barack Obama formally accepted the nomination, you have to wonder if Brolin anticipated humanising George Bush onscreen to the point that audiences would find him sympathetic?

He admits he came to like Bush as a person, though not his leadership. "He grabs you, slaps you on the back, says: 'Let's go have a beer.' I understand it, and he wanted to get away from this elitist, untouchable thing of presidents in the past."

Brolin's stepmother, famously also a keen Democrat, has yet to see the film, although as one of Hollywood's highest-paid singers and actors, she did take a keen interest in one aspect of Brolin's work.

"When I told her I was going to play George Bush, her first question was 'How much are you getting paid?' I said: 'Nothing.' 'Then why are you doing it?' she said.

"There was something written in one of the rag magazines that she'd thrown a fit and wasn't talking to me. I kind of liked that – but actually I think she was very pleased that I was doing something with such weight." v

W is on general release from Friday