I don't clean their mouths at all, I didn't even in the beginning. Their mouths don't get messy either - but then, I don't feed prey model. But even if I give a bone for chewing, I just wipe them off.
And, just to further gross everyone out - I really don't worry
a whole lot about how much time has passed after they've eaten for their kisses either. There are a lot of things that are killed via it being frozen after all. I'm careful, but I'm just not that worried about it - to be honest. And I've never had a single problem with it.
Also, there is FECAL MATTER all over our paper money (just to name one thing) - so, what are we gonna do? That grosses me out more than the raw meat....