After cleaning my brushes in thinner or mineral spirits, or emptying my stain pot, I pour the liquid into a can filled with sawdust. The sawdust absorbs the liquid and at the end of the week I toss it. In fact I keep two can of dust,one for the liquids and one for the container that they came in. After I pour out the liquid I am left with a residual amount of whatever was in the container, I add the dust and stir it around the insides until there is nothing left, swab it with a paper towel, ready for a new job.
-- honing my craft one mistake at a time.