If you are concerned about the MAF sensor, it takes a can of MAF cleaner and 10 minutes to clean both sensors.
I cleaned my K&N filter recently and was thinking of going back to OEM filters before I started. While busy cleaning the filter housings, I realized how super clean, dust free (no spec of dust) the clean air side of the housing was. Needless to say, the K&N's went back in and decided I can live with the microscopic things that goes through.
The bigger concern is over oiling the filter. I normally use my heavy duty shop vac to remove any access oil from the filters. My theory has not been tested but I suspect its unlikely that a car will have more suction through an air filter than the concentrated suction from a heavy duty shop vac, so what is left in the filter will stay in the filter.