Here's the finished vinegar/iron wash. After a week in the vinegar, the iron was completely dissolved. I lined a funnel with a coffee filter and poured the iron wash into a clean glass jar. Here I've put a few drops on a white plate so you can see the reddish brown color. This stuff will stain things like paint and formica, so be sure to wipe it up right away if you spill any!
And here is the quebracho bark tea. It's much quicker to make than the vinegar wash; you simply stir some of the powder into very hot water and it's ready to use. In Brian Boggs's article he lists a taxidermy supplier as his source, but I bought my quebracho bark powder from http://www.shellac.net/Dichromate-Tannin.html because they sell it in smaller, half-pound quantities. I think the small packet I got will serve me well for years.
Take a bit of extra care in removing the sanding dust. Here I use a wide paintbrush (dry) along with my vacuum. I sanded as directed in the article. One point Boggs emphasizes is that you want to avoid burnishing the wood. Too much pressure, and sanding to a too-fine grit can cause this burnishing, which prevents the washes from penetrating the wood deeply enough.
Fantastic! I'm a believer.
In the article, Brian warns against letting the two washes touch each other anywhere other than on the wood, because they'll react with each other outside the wood and lose their potency. I was very careful about this. I used two separate cheap paintbrushes, one for each wash, and frequently rinsed them with clean water to be sure I didn't start getting the washes reacting with each other in the brush.
I let these washes dry for several days, pinned the back slats with dogwood pegs, then finished with Waterlox as usual. Here's the finished chair, complete with a riveted leather seat: