: Unless the air compressor is truely oil free I'd recommend to not
: use it

It makes sense to assume oil is in the compressor air and to wash with soapy water afterwards. And as all the other techniques mentioned are more readily accomplished, it’s really a technique of last resort because it assumes a compressor or junk fridge compressor and hose with syringe needle.

However as a last resort, needle(syringe) directed compressed air flow is a technique I’ve used to complete success on 100s of disgusting almost microscopic whitened pinhole situations when all other approaches mentioned fail. ie: finest brush, thinnest wire brush, individual needle point digging, vacuuming, blowing, compressed air gun nozzle, washing, individual syringe pumping, power washing, dental pik (ie directed thin water jet used for cleaning between teeth), swearing, crying, jumping up and down, and basically wondering what the heck to do next.

It’s quite fascinating and heartwarming to see the dust completely disappear in a small puff when the directed air sets up a mini whorl in each pinhole.

So if one doesn’t mind the extra step of a wash up, it’s an amazingly effective technique when all else fails.