I was also wondering about Feliway. I like the idea of the child locks on the cupboards! Although I can't say I've ever heard of kittens being so naughty. I'm sorry you are having this problem.Kush--have you tried Feliway or added Rescue Remedy (liquid) to their food?
OH! one thing, I don't know if it will work, but my vet tech swears by it, but depends on the cat. SOME cats, when you put a harness on them, decide it's time to go boneless. That's a good time to try to clip nails...IF your cat does that.