Take something like a credit card and gently open the snakes mouth and keep it there so he can't close his mouth. Then take a piece of paper you folded several times so it's not flimsy and just kind of brush it out his mouth. Do it gently though. I do this when mine get aspen in their mouths and I've never had a problem. It's not as easy as it sounds though and you have to be careful with the tongue and gums and all.