This has been dogging me for months and I finally have it figured out, well I haven't tried it yet but at least I have a recipe.
I have a large painting commission that involves a lot of text. I wanted to transfer it to the canvas rather than hand letter it all. I did this in college but couldn't remember all the steps involved. I have done google searches and forum posts to no real avail aside from gel medium transfers and the citrasolv xerox (toner) transfer method found here, which is akin to methods using acetone or wintergreen, but I was looking for something that would transfer ink that would stick to the toner on the xerox so the image color could be changed and matched to painting. Seems someone may have been looking around the time I started my search and was as desparate as I, only she looked in a printmakers' forum where she got the answer below. There is also this newsletter article which outlines the xerox lithography technique as well. The research is done now on to the experimentation phase, and to the art supply store for gum arabic, the magic ingredient missing from my memory. I am so relieved, deep breath in----deep breath out.
Below is a concise overview for reference, thanks to Mr. Maestro Nick.
1. Make a fresh xerox
2. You want to make a thin gum solution, so add 1 part gum arabic, 1 part water in a bowl.
3. Use a sponge or sponge brush to wet the copy onto the glass with toner side up. It needs to be wet, but the paper will degrade if you do too much. Just enough to wet it. The gum will help to protect the open paper. Be gentle.
4. Roll up some oil based ink and roll your brayer over the copy gently. It might roll up with your roller so start from the center and roll to the edges.
5. You need to keep sponging to remove the excess ink and to keep the copy wet, so sponge, then roll, then sponge, then roll.
6. The toner will appear glossy from ink when it's ready. Sometimes this is very quick.
7. Once it's wet, it's very fragile, so be careful when peeling the inked copy off of the glass. Run this through the press onto paper or fabric under some good pressure. I usually set it on a plexi plate, but you don't have to.
Hope this helps. It's called xerox lithography if you want to search elsewhere for this.
Best of luck! When it works it works great!
INKubator PRESS, Kansas City, MO