What DOES he care about? Start there and work backwards, but taking away things they care about isn't always the best discipline. I used TV with Oscar for a while and it backfired and he started obsessing about watching "his shows." Now that I don't use it as a thing "to take away or reward with" he's much less TV-obsessed.
And sorry Cosmosmom, but washing a kid's mouth out with soap, hot pepper, or anything else is a violation of personal space and isn't going to do much but teach a lack of trust and potentially damage their spirit. IMO.
He sounds like he's certainly being a booger - but you can find ways of keeping him in check (or just dealing with it when nothing seems to work, because sometimes, no matter the kid or mom, nothing DOES). Sounds like things got better.