Do actors typically use their tongues while making a ki-ss-ing scene?
It depends on what the scene requires. In scenes like when a couple ki-ss-es in front of other people there won’t normally be any tongue. In scenes where the characters are sad and talking, they might share a passionate ki-ss, but normally there won’t be anything more than that.
Tongue ki-ss-ing is normally used in more romantic scenes, where the characters are alone and getting in-ti-ma-te. Please note the word “normally” as there are exceptions.
When it comes to the actors, they know what to do when shooting a scene because there is a lot of planning and rehearsals. When the director yells “action” the actors will do what they previously agreed to do and what they expressed to be comfortable with doing. If an actor tries to stick their tongue in another actor’s mouth without it having been agreed to or discussed beforehand they could be in a lot of trouble.