Power Steering Bleeding?

1999 Sable: Problem started when I agreed to have the system flushed while the car was in the garage for another problem. Picked the car up and pump was making "growling" noises under loading , also fluid is being forced out the reservoir cap. Garage said the pump was shot. Had enough of them and replaced pump myself. New pump..same result. Drove car for about a week thinking it would bleed itself. Removed reservoir and cleaned it thinking screen was plugged. Now the steering is harder and air is being forced into the reservoir. Read in another thread that bleeding this system is a pain and can done with a vacuum pump.
Is this true?..if so, which side should I bleed from.
If not, what should I do next?...

Could it be possible that your rack and pinion is bad? You have a crack in a seal or something somewhere on the rack and it could be sucking air into the system and back into the reservoir.

I don't see any leaks form the rack, but can't be positive that it's not sucking in air though

When you replaced the pump did you notice any debre in the fluid? It may be possible that you have something stuck in your high pressure line and the pressure relieve valve is pushing all the fluid back into the reservoir causeing it to overflow.