Assuming dry paper, just tap it on a hard surface (relatively gently) to
remove loose stuff then use compressed air from the inside out (only) and
it'll be "good enough". Don't get it wet, it'll turn the dust to mud and
plug it for good.


Compressed air can drive particles of dirt thru the filter leaving holes in
the filter for dirt to enter the engine. I tap mine gently to knock off the
loose stuff. Then I wash with soap and water. I repeat this several times
before buying a new filter.