OK, I was wondering if you guys "seal" the paint on a model before doing a wash. I know some of you guys say to use future, but I have no idea what this is, or where to get it. Any help appreciated. Thanks!

Future is an acrylic floor polish by Johnson's. You should be able to find in in the grocery store or box department stores. It's pretty self leveling and can be airbrushed or brushed on.
Using this will reduce the possiblity of a wash attacking a base color, even if the same type paint is used. It will also make the the wash stay in hte lines more. A wash, judiciously applied with a file brush and no scrubbing or dragging will not harm even same type paint. It may tend to spread out a bit more, giving more of a shadow effect.