The key to dealing with these maniacs is PATIENCE. Don't be tempted to call his raises with hands like A5 offsuit just because he has been raising with much worse and getting lucky on the flop. Wait for hands like pocket pairs and suited connectors (in position) that can flop a massive hand. If you do flop a huge hand, LEAD OUT against this guy if he will always raise your flop bet then RE-RAISE him to try to get him to shove over.

If your hand is not vulnerable to draws (eg. nut flush on a non-paired flop, set on a rainbow, widely spread flop) then you can slowplay a little bit if he will aggressively bet every street.

Don't bluff against this guy. This is just throwing chips away.

If you pick up a decent hand preflop (say 99+, AQ+) be tempted to re-raise or shove over him since he is clearly raising much wider than that. If he calls your preflop shove with something you're ahead of, you very likely get your chips in when you're a 65-70%+ favourite.