You need a big enough roll to play against these guys without jeapordising your whole session by being out after 2 o r 3 buy ins.
I used to play with two buy ins and effectively if I didn't have a monster preflop I'd just have to fold and therefore it is better to find a new table. I should say even then 99+ AQ+ was more than enough for me to 3bet gii vs this sort of player.
Don't give them too much credit either. If he's an affable chap and enjoying himself and getting a decent run of cards and being folded to by some idiot with 2-pair on flop (WTF????) then he is going to look like a poker genius.
He is not a poker genius, he is just a guy having fun running people off their hands with someone else's money he doesn't care about. Get in there and gamble with him!
I find it helps to engage with maniacs like this and show the same joy at throwing your chips about as they do. He'll be least likely to adjust if you give the impression of being like:
"oh if it's that time of night let's all gambooooool!
"
Rather than:
"don't you realise how bad I'm going to own you when I get AA???
"