I have never done this, but plan to when I am finishing the assembly of my engine. I have read in a couple of places that if you take some white spray paint (can be a cheap type) and spray 2 or 3 coats on the outside edges of the copper sandwich (FelPro type) gasket just before installing it, it will prevent the unsightly water/antifreeze stains down the side of the engine. If a little paint gets on the top or bottom of the copper, it doesn't matter. Another thing I have read about several times is, apply some gasket sealer on the water jacket holes in the head gasket. This helps prevent water/antifreeze from seeping into the inner part of the gasket and out the outer edge of the gasket and down the side of the engine.
Rusty Nelson