Masturbating and wanking.
Any others are frankly just stupid, especially when using multiple words for it. People get what you mean, it isn't being creative or funny or interesting in any way. In fact the only humour that comes from it is when people say something unsexual which sounds sexual by accident which they didn't realise would happen and from that the humour arises. Trying to force that and doing it on purpose is boring and bad.