You actually need to apply a vacuum instead of compressed air. The new compressor should be loaded with about two ounces of refrigerant oil. Once the new compressor is installed it should be turned by hand for several complete revolutions to distribute the oil and prevent compressor damage on startup. After that, the system needs to be evacuated and held at 27" Hg or greater vacuum for a minimum of ten minute to help remove any moisture in the system. If the accumulator has been cleaned out the remaining oil charge (about 4½ ounces) should be added at this time, then refrigerant can be added. System pressures on both the evaporator and condenser need to be monitored when adding refrigerant to make sure safe pressures are not exceeded until the system is completely charged (by weight).
It would be a very good idea to remove and clean out the accumulator and to remove and clean the orifice tube or just replace it (about five bucks) when replacing the compressor.