A Scat Wank involves the "wanker" convering their penis and testicles(maybe even whole body if desired) in faeces. Then they should "rub one out" so to speak with ones fallus covered in excrement.
Male 1: "Yo dude, have you heard of this new craze which has hit America?"
Male 2: *Shocked expression* "Wow what is that?"
Male 1: "It's called scat wanking."
Voice over: "Scat wanking is avalable for anyone wherever they are...but if you go to an organised party forget Bring Your Own Beer the new phrase is 'Bring Your Own Shit'"
Small Print- * We (The Government) do not hold responsibility for Aids contracted in the pool, from shit dick or from a scat wank.