Torrey, If you can find a friend with a real grinder, the kind that gets up to 12 or 13000 rpms. Buy a good stainlees steel wire brush for it, they cost about $10.00.
I have been through the same thing with my Scamp
. I tried the chemicals and brushing with drills nothing worked until I used my Makita grinder with the stainless steel wire brush. The grinder is not only quick it does a great job.
It will create fiberglass dust and other stuff in the air I would advise wearing a mask and eye protection.