A soft rag and dish soap in warm water.
Yes they can. You are supposed to leave the place like you found it. It is also a good idea to take photos of the place and date your photos so you can show what it looked like when you moved in.
Snazaroo is the best and very expensive. If you need to practice, use watercolors in those little pallet cases. I have also used my acrylic paint and just thin it down a little bit. Dries really good. Go to ebay they have tons of sizes and prices.
You need to buy Scott's Value book or the" official Blackbook Price Guide To United States Postage Stamps". Those books will tell you everything you need to know. sandypal stamp collector