I had a kitten that did the same thing. He had a white teddy bear that he sucked on when I got him, that was taken away and then he started to do the same drooling motion around me and my clothes. It's a motion they get as kittens with the mother's milk. When taken away too early, they attach to something else (aka shih tzu or bear doll) trying to satisfy that need for milk. I would try finding a cat toy/doll, introduce the kitten to it and then when he starts to suck on the shih tzu's hair place the doll near there/instead. He may then, gradually, attach to the doll instead. I tried this with my cat last year with a random medium sized white seal doll that was like the bear. Everytime he tried to drool on me, I subtly put the doll between us and he has picked up to go there when he wants that comfort. Try also, a doll that has the same texture as your shi tzu. This may help in transitioning.

I think only time will stop this. We have a shitzu(hal) and 2 cats. Hal "protects" the cats from everyone and plays with them all the time. I figure it has something to do with being similar in size.