Use Waxed Paper to Prevent Skin on Stored Paint

To prevent unused paint from forming a skin, trace the paint can lid onto a piece of waxed paper. Use the top of the lid, not the side that the paint is on. Cut out the waxed paper and place it directly onto the paint.

When you use the paint again, simply shake up the can and you're good to go. Do not try to remove the waxed paper, it only causes a mess. (Learned that the hard way.) Just ignore the paper. If paint is still left over, place new waxed paper onto the paint.

Works like a charm on latex paint. I have not had occasion to try this with oil based paint.