Wrong power steering fluid

[MisterAl]

Hi, I left my 92 Lsl sitting outside over winter (Canadian). She started up first turn of the key a few days ago, but here was no power steering, and I found the reservoir was empty. I needed the car and without thinking, I found I had a can of regular power steering fluid, the kind that suits Gm, Ford, Chrysler etc (no other specification was on the container), and filled up the reservoir. I have only run a few miles since and the steering is moaning somewhat but working, so I guess the fluid is still leaking out.
My questions: 1) Have I done any damage because of using the wrong fluid? 2) Will just flushing out the system with ATF be sufficient?
Any help would be appreciated.