Vaseline? How in the world do you do that? And how much do you give the unlucky animal?
When I clip her claws, (once a week) I reward her with a little vaseline. I usually just take a little glob about the size of the tip of my thumb, and spread it on a foreleg or her tail. She will lick it off.
I had a cat that BEGGED for vaseline, but Hobbes doesn't. She likes it, but she's finicky. So if I put it on her fur, I know she will lick it off, and therefore, she will pass the hairballs.
A lot cheaper that "hairball formula" foods... A small jar of vaseline (any petroleum jelly) will last a year or more.