That 'wood bleach' or 'deck brightener' is oxalic acid as the active ingredient.
Hey 'jerrykr', what kind of wire brush(s) are you using, we know they are not all created equal and I'd hate to see somebody just go out and buy something too harsh (way too easy to do).
I use several myself, from fine brass up to a coarse steel wire, and a key to use (for me, anyway) is to start 'soft' and move coarser as needed, letting the tips at speed do the work while hanging on TIGHT. Its easy to concentrate on the job the brush is doing and loosen your grip on the stock!
One of the best tips I ever got was to use a scraper (or, in this case, brush) that is a softer material than that you are working on, to avoid scratching.