If you do try to learn probing from a video or website, sometimes they'll say it's enough to lube up the probe with water....it isn't.

if you do that, you run the risk of either tearing something inside the snake because it's not lubricated enough, or you can get a false female result because you don't think the probe is going in very far. Mineral oil is my stand-by, and I've heard KY jelly works, although I don't know if the snakes would get any enjoyment out of the "KY His-n-Hers Warming Sensations" or whatever it is...