Compressed air --- from a real compressor, not a can --- but it needs to be Dry,
so, if possible, there should be a water trap in the line.
That plus a vacuum cleaner and a cheap "chip" brush
should get rid of most of the dust.
For really dirty equipment, it's hard to beat Dawn dish detergent (the plain version, not any other)
diluted in water and applied with anything handy for the task such as Q-tips or rags.
Of course, the equipment should be thoroughly dry before it is connected to power again.
Ages ago, a friend who had a repair shop had to deal with an especially dirty TV set.
He removed the speaker, then he literally turned a high-pressure stream of water
on the inside of the (plastic) cabinet.
It did the job, and once the water had dried up
he reinstalled the speaker and proceeded with repairing the unit.