Darrel, a/c compressors - both old and new - are typically flushed by the following procedure:
- Remove compressor from vehicle.
- Hang compressor so lubricant drains from it. Rotate the shaft every once in a while to get as much lubricant out as possible.
- Pour in some new fluid. Run it through the compressor by rotating the shaft. Let that fluid drain.
Don't use compressed air in the compressor.
If you need more help with your a/c I recommend posting questions at aircondition.com
, a site devoted to automotive air conditioning systems.