I have two comments after reading this whole thread (and checking out a lot of links in it).
1) Oxyalic acid is wood bleach. Wood refinishers use it for getting stains out of old wood. I imagine it wood (pun) work, and it is not as strong as chlorine bleach.
2) I'm wondering if this product (Poli-glow) will be a problem down the road when someone wants to re-paint. When I painted cars, we always had problems with any car that had a "poly" product on it. It took a special product called "Poly-cracker" to get it off and added to the cost of the paint
Just wondering -