The one bit of success other than the constant repetition, that I have had is a teething ring clipped to the shirt which the child is allowed to put in his/her mouth, lick, suck, chew on, whatever floats their boat I started this with a child who was starting to bite...he had always been an extreme mouther...as soon as I started with the teething ring, he stopped biting and the mouthing decreased drastically. He needed to get those oral urges out somehow, so I gave him an outlet. It could help for some of our extreme mouthers. Not sure it would help for thumb or finger sucking though...my 3 and 5 year old suck their thumbs...nothing seems to work!