If it were me, I would try placing the sub so that the plate/volume knob was upright, then remove the knob and squirt straight down the potentiometer shaft (keep your comments to yourselves, students). Put the knob back on and turn back and forth 20X. I can't imagine it would hurt anything if you don't use too much.

Of course, just because I would do that doesn't mean that I'm recommending that you do! \:\)

::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::