Just use five minute epoxy. It's used all the time to coat eyes on latex masks. It has a natural SLIGHT yellow glaze after a little time and you can add tints to it to alter the color. You could mix it up and brush it into the snout, giving a thin, wet, covering like an eye and then (with a new batch...) apply a thick strand to the mouth. Maybe even let it drip naturally to achieve the drool look.