Vacuum out or blow out the dust from the equalizer panel with compressed air, while slowly moving the sliders through their full range. This action removes any large dust clumps. If a slider is completely stuck -- don't force it.
Spray a contact or chemical cleaner, preferably one that doubles as a lubricant. If you can't find one, use the chemical cleaner first and apply a lubricant after it dries. The lubricant should be lightweight, as thicker chemicals can build-up inside the amplifier and attract dirt. Move the sliders through their full range while spraying to distribute the cleaner and the lubricant, if applicable.
Put on your safety goggles and blow out the dirt and cleaner using the compressed air. Move the sliders completely up and spray the compressed air, before moving the slider down completely and spraying again. This will ensure all foreign components are out of the mechanism. Allow the chemical to dry and test the amplifier sound.