I have used a resusable portable douche kit (very small balloon) with water to rinse things.. it's 'a n a l'...not colon sex. sit in tub, warm water in the balloon, rinse, finish over the toilet. seems to work just fine. also...if he is wanting to do this, has experience, well, things happen and he's most likely prepared to deal with it. if not, he shouldn't be doing it.
as far as the diet, I haven't been able to know in that much time if my guy and I are meeting up. good luck