I was so nervous too, but you have to relax! You are going to get to bring your baby home, enjoy it and don't stress. For now a mild puppy shampoo will do nicely. I would not advice you to wash him too much because then his skin may dry out. Im not sure on the brush, but I have a pin brush that is pin on one side and soft on the other. Even though he is a puppy, I still brush him daily. He hates it, but he needs to get use to it. I have not had to cross the bridge of how to care for his butt yet because he hasn't had any issues in that area yet. I hope I eased your anxiety a little bit and I know that there are many people on here that will be able to help you further. 
