For my Border collie, all I have to do is give the command "Kisses" and point at what he is to lick, if its moist, he will definitely lick/kiss/eat out whatever I have pointed to.
I really need to find someone thats open to experimenting with him, as he has just started to fuck me, and I want to continue encouraging him
Praise them when they lick, but also let the interested party know that they're dealing with an animal that may or not may be in the mood at the time. That being said, in my experience a dog that gets the chance to sniff or lick a pussy, will almost always be interested, even if just for the new scents, we all smell and taste different.