Don’t store leftover latex paint in the can it came in. Mold and mildew can form inside opened paint cans, ruining your leftover touch-up paint. Instead, use squeezable plastic jars from pantry staples, like ketchup or mustard. Give them a solid cleaning, and pour leftover paint inside. Add a glass marble or two, too. When you need paint to touch up a scuff mark, just shake the bottle (the marbles help agitate the paint) and squeeze. Just enough paint will come out to get your job done in no time flat.