woodbowl: I did a Google search for "weathering wood" and it was mentioned in some of the top results. Apparently they use it in the model railroad hobby for some balsa miniatures. I saw it mentioned in other places as well, from distressing antique furniture to ebonizing oak, etc.
The steel wool dissolves in the vinegar, given enough time. I suppose you can let it partially dissolve and place the remainder of the steel wool in a new batch of vinegar.
Thankfully the process doesn't require precision as far as quantities or time. When doing the house staining, I'd use 32 oz of vinegar per 1 steel wool pad, and let sit overnight... but I find that you can really change the ratios and amount of time quite a bit.
Lately I'm experimenting with building rustic picture frames. In some old redoak barnwood, I've found out this stuff works very well for the parts of the frame where you have fresh cuts (like the inside parts, where the pink shows up). I simply rough those parts up with a wire brush / rasp, etc. and apply a special low-concentration version of the mix(because too much will turn oak black). It really helps blend the new cuts with the rest of it, giving the whole picture frame the barnwood look.
Another variation I've tried is a version mixed with india ink. On some pine the standalone stuff gave greenish tints. The ink helped tend it toward grey.
