I don't recall the ratio used but here is before and after pictures. Did this back in 2009.
Colnago Fork Crown as bought on Flickr
P9161264 on Flickr

Bought the Oxalic as granules in a small container at the paint store, Sherman Williams IIRC. Still have some left. For the fork, I used a wallpaper soaking tray. I also built a 2x8 frame joined with hinges as a tube using in black Visqueen as the liner. The hinges allowed me to soak different size frames.. Use cinder block or something else in the spaces of the frame to minimize the amount of fluid. Let it soak overnight. No damage to paint or decals. The missing paint on the fork was from another mishap by a PO.

If the solution is too strong for the amount of time soaked, it will leave a white residue.