If the ESC is waterproof you can submerge it too! All brushed motors and sensorless motors are waterproof by default... with the kicker that you need to clean and oil any motor and bearings/bushing after it has dried.
Any liquid will work, idea is that you want to soften the brushes so they can be re-shaped easier, that's where Trinity formulated their comm drops to be more effective in softening the brushes than water. I have no idea if AF does a better job, but I have heard of others using it. I have yet to...
Chances are you may have already damaged the brushes on your motor if you didn't break it in first, small chips of the brushes will break off and you lose significant contact patch with the comm and that reduces your performance.
I've had really good luck with the Trinity Black Death Comm...