Burnish the Corner
If your baseboard or crown molding has a slight gap in the outside corner miter, you can hide it by rubbing the tip of the miter with the shank of a screwdriver or nail set. The bent fibers will disguise the gap, and the slightly rounded corner will be less likely to get chipped or damaged. The best way to prevent this problem is to cut your outside corner miters about 1 degree sharper than the actual angle so the tips of the miters touch. This will leave a tiny gap at the back of the miter where it's barely noticeable.