Yep, lipsmack-smack-smack-smack is totally international simian for “relax and get your fur picked”. It’s a very friendly sound.
Mouth-to-mouth-with-tongue kissing’s usually guessed to be related to food sharing, but kissing everywhere else is probably left-over grooming behavior in humans. Along with stroking and patting and playing with peoples hair.
Cat fur must be stimulus overload for a little monkey like that - lovely thick stuff with lots of tactile feedback 
