I read about a session and the reviewer talked about p2p.  I looked it up because I could tell it wasn't what I thought it was in the context the reviewer was using the acro lol.  Anyone try it?

It's shorthand for privates to privates. And yes I have.  The idea is rubbing/sliding your private parts gainst her private parts, but not penetration. Obviously less safe than covered, and of course this requires both parties to agree to it.  
I have done it only a few times with girls I know very well.