Hello,
I have some experience and I must tell you I'm against Douching. It has been shown that it increases your risks to catch a disease because it removes some of the lining making you prone to catch something by removing your natural bacteria living in you. If your plan is to have sex it is better to not eat so much the day before and take a good dump before. Maybe take a laxative if you don't poop regularly.
Also, it might be painful so foreplay is highly recommended. a lots of water based LUBE... this also offers some protection.
FINALLY use a condom.... even though the other person might not have HIV...there are other diseases that are not good for you.
if you decide against using a condom....take a poop after you get it, especially if he cums inside you... you really want to minimize risking getting a disease.
hope it helps...