To cup (not grab, cup) someones buttocks and yell, "Peaches!" If you successfully 'peach' the person, you yell "Got 'em!" If you slap someone instead of simply peaching, it does not count as a peach and therefore you did not completethe process of 'peaching'.
After an individual takes a very satisfying shit on the toilet, it is essential for them to wipe. If you begin walking after taking a shit and a few pieces of shit or "muddy water" fall or drip down your leg you are by defintion "peaching off crumbs."