ive tried it before and it feels weird but it turns me on big time
1. get a funnel and a liquid... preferably water or milk
2. strip down
3. lube the thin end of the funnel and insert it into ur ass
4. slowly pour the liquid of choice into the funnel and let it run into ur ass
5. for a diff type of experience, heat the liquid to a lukewarm temperature
6. when done pouring liquid start jacking off and slowly let the liquid run out of your ass.
little advice if you try this... do it in a tub or somewhere you dont mind getting dirty and wet. because this gets messy