Too close for the usual advice - read a couple of good books - then

You only have poo in the rectum (the area where a penis can reach) when you're just about to go to the toilet. So go now, if possible, and don't worry about it. If he wanted spotless, he wouldn't be asking for anal.

If one of you does want this to be as near spotless as possible, it's enema time (luke-warm water only). It sounds like you don't have anything to do this with though.

Many people find it's messiest when you next poo - the leftover lube making the poo sloppier.

Some people charge more, others don't. It's up to you.