GUIDE : cum sharing, also known as snowballing. Imagine you just came into your girlfriend's mouth. Then she wakes up, and starts giving your second girlfriend a french kiss, or even better, she simply lets the cum drool out of her mouth into the second girls mouth... that's what snowballing is about. Warning : cum sharing is VERY arousing, although it's quite difficult to do it at home.
VISITOR : why ?
GUIDE : well, sir; ever had two girls at once ?
VISITOR : uh... no
GUIDE : OK, that's why it's so difficult to do : most of the time, you only have one girl at once in your bed, and when you have one, it's not always easy to have her swallowing your come. So imagining you have two girl, wich is possible (It happened to me ONCE in my life), you still have to be lucky enough to have them being TWO cum-swalloing gals : mission : impossible