You can also purchase a douche intended for vaginal use, dump whatever solution is in it and replace with roomish/warm temperature water.
I've read recommendations to do it a couple hours before you plan on, shall we say, being in an active state of mind?
If you're just planning on doing a little exploring rather than penetration, cleaning yourself in the shower might suffice.
And speaking of the shower, I've also read that some people like anal play in the shower because anything that isn't perfectly clean can get promptly washed without much ado. Personally, I'd be worried about slipping lol.