If you all do not watch him, I highly recommend Alton Brown's Good Eats. He essentially dispelled the myth about washing the fresh mushrooms. I believe his experiment showed they did not appreciably asborb moisture. I usually just brush mine off though. I also recommend watching his technique for sauteing them. I am the one who popps off the stems and dries them. When I get a good bunch, I grind them to a powder in my spice grinder. I add them to soups and sauces all the time. My in-laws grow shrooms, shitake, crimini and button. They get those plugs you put into a log of hardwood and sit back. Works great and I get loads of them, fresh and dried. I have a few food allergies and I am a chemist, so long ago I started cooking mostly from scratch. My wife would thump me but good if I ever tried to serve her canned cream of mushroom soup. I make it from scratch and it is one of those dishes to get me out of trouble. (we have it a lot.)
I have mixed some powdered milk, chicken bouilon, mushroom powder a little cornstarch, salt, peper, and dried onion and garlic for a friend who likes to backpack. Add water and heat, he raved about it.