ski bum

You will need to open up the amp so you can spray the cleaner into the slot above the 3 electrical contacts of the pot.  There will be two sets of 3 electrical contacts on a dual-ganged pot, and hence two  slots to spray cleaner into.  If you have a pair of single pots, then each pot will have a set of 3 electrical contacts and a single slot to spray cleaner into.

After trying just about every cleaner under the sun over the past 20 years or so, the one I've had the best luck with, both for instant and long term results, is WD-40.  It will clean the crap out of the pots, lubricate them, and won't evaporate instantly.

DanK