I recently cleaned an old soundcraft live 32 ch mixer.
this what I did:
1) compressed air on each fader
2) deoxit faderlube spray 5% on each fader, then thoroughy move it up and down for at least 1min
3) deoxit faderlube drops 100% on each fader, then move it up a couple of times to spread it
4) deoxit spray 5% on each input / ouput (XLR, jack, etc)
5) deoxit gold spray on each input / ouput (XLR, jack, etc)
works like a charm now
I also opened it and with a small vacuum I gathered all the dust inside.
If you're patient enough, you can also do the same with faderlube for each knob
