1. Even if it hurts, will my body be okay with 7+ inches? 2. How can I get everything clean down there? 3. Does taking two penises at the same time work?
Your body will be fine based on several critical elements. 1) communication with your partner. Let him know what you want and 2) when to slow down. Some of us get too excited and press on, to our peril. 3) Lubrication. Lubrication. Lubrication. There are lots of good products, some of them quite arousing in themselves. Some of us use enemas or anal douches. Can't answer # 3.
Note: Anal douches/enemas remove the protective mucus layer in the anal cavity which can increase chance of fissures and STD's. Just an FYI to the OP if he is not already aware of it. Proper diet and planning of bowel movements makes douching completely unnecessary IMHO.
It should never hurt. If its a larger penis, then you need more prepping, more lube, and go slow at first. Some people finding using a butt plug helps them prepare. Yes its okay, but it should never hurt. Start making sure that you have a high-fiber diet. Try to learn your bowl movements and you shouldn't have a problem. You can douche, but like it was said above, if you have a good diet and you take a shower you should be good. What do you mean by work? Is it possible? Yeah, but it takes patience and working yourself up to it. It also takes tops that know what they are doing and respect you enough to take it slow and not just ram them in. Use protection!
These answers I'm about to answer are based on my opinions and experience: 1. Your body should be able to handle 7+ inches long if it's able to. Depends on who you ask and how your body can take it. Just got to relax and feel comfortable enough to take it in you. 2. There are many ways to get clean down there. Use a douche cleaner or something similar. Sometimes it works using your bare hands if you need to be comfortable with yourself by using soap and water. 3. Again, depends on who you ask. Some people can, some people can't. But for me, I wouldn't be able to as my body is not capable to take it more than 1.