To keep excess stain or finish off the rims of my quart-size cans, I stretch a thick rubber band around the can from top to bottom and across the opening. That way, with each dip of the brush, I can skim the excess liquid back into the can without ever touching the bristles to the rim. I keep a couple of spare rubber bands on my finish cans for this purpose. The rims stay clean so the lids are easy to install again.
– Charles Mak