DO NOT USE EXTREMELY HOT WATER!
If you ignore that, this is what will happen:
*Paint on knob markers will be removed. (Do not use solvents to clean knobs!!)
*Slide switch has a piece of paper that acts as a very necessary dust cover that can be warped. (Can also be warped by solvents.)
Replacing is difficult to do (see below), so do all you can to avoid damaging the paper.
Get 1 side of switch wet w/a q-tip and flick switch over.
Disassemble switch with mini channel lock pliers and flatten the dust cover via iron or vice
*The resistive elements of pots (esp 1 meg) can be damaged