If you do a lot of polyurethane finish work, here’s how to avoid cleaning your brush after every application. Slice a 1-in. “X” into the plastic lid of a coffee can to hold the brush handle so the bristles are suspended in thinner.
When varnish residue builds up to an inch or so on the bottom, pour off the uncontaminated thinner into another can and start over. You’ll rarely have to clean the brush and will save lots of money on thinner. You can dispose of the residue by letting it dry, then throwing away the can. Thanks to Jim Pearson for this tip.