just treat people like human beings and that's it. if people really complain about you because your character is rude, then don't bother with them, since they should be old enough to know the difference. i love rude characters myself, and although i joke saying "i'm rude because my character is" from time to time, most people have stopped complaining.

your character's expression can work. things like looking at people with disdain, folding their arms across his chest, or just being kind of passive aggressive work perfectly. of course it all depends on the character, review a few bits of your character's canon and check their attitude towards people, their movements and stuff. it should give you a good hint.