If I hold my hand behind their heads and very gently stroke the softer fatty parts on the back sides of their head, they will sit still as long as I do it. Either they like it or it somehow sends a message to them that they should hang out until it stops and then it's safe to move on.
Interesting! I'll have to try that. All my snakes are a little head shy right now. It would be nice to break them of that.