I think the only way you can break a child of this habit is if they want to stop it also! Otherwise, you're fighting a losing battle!
That said, if you do get the child on-board, I think hot sauce is mean too (and what if he rubs his eye afterwards--Yikes!).
I broke my daughter's habit right before she turned 5. She was tired of being called "cry-baby" at preschool, and the thumb sucking wasn't helping any,
We rewarded the heck out of her that first month! We set up a reward chart. She got fifty cents for each day she didn't suck, a present at the end of each week not sucking, and a really big present at the end of the month. We did a second month as well, but dropped the fifty cents/day part.
In addition, because putting the thumb in the mouth is something you do without even thinking about it, we taped her thumb to remind her if she forgot. This method worked like a charm. I think she was pretty much done sucking by the first day! She loved her reward chart and all the cool things she got for stopping!
Don't make it a power struggle, because you won't win!
Good luck!
C.
www.littlebitquirky.blogspot.com