I agree with both techniques described, and do feel that opening a snake's mouth should be done at time of purchase, or upon receipt if it was a long-distance transaction. I prefer a rounded needlepoint needle to a toothpick though, to reduce the risk of a splinter or the toothpick snapping if too much pressure is used. Not that pressure should ever be applied!
You want to look for signs of mouth rot, parasites such as flukes that are clearly visible on the roof of the mouth of an infested individual, or any injuries.
It's important to know about any problems before they blow up into a huge condition. I figure they are already stressed by the change of scenery and the trip, so one brief 10 second inspection isn't going to trigger too much additional stress and can be quite useful.
The Zombie Mama is here!