The local swap meet yielded a very inexpensive front wheel with a narrow WOLBER SuperSomething "Alpine" double-wall rim, nice and true. Unfortunately, the cones were badly pitted.
I mounted one cone on the axle, slipped the axle into the drill press (a drill mounted to be stationary would do fine), coated a couple of cm of 1/4" (~5 mm) wooden dowel with valve grinding compound, turned on the drill press, and pressed grinding compound against cone. I rotated and moved the dowel around, and it worked pretty well. The surface looks like good ground cone surfaces -- except that I didn't go for perfect. I think the key is that the wood gets grinding powder embedded in it (like diamond chips in a metal blade, so it keeps grinding (and I occasionally refreshed the compound). Took maybe 5 minutes, which compares pretty well with the time I would have spent trying to find good cones with the right threading in the parts box.
In this case, I didn't have the option of easily repacking the hub with grinding powder and spinning it, since it was a complete wheel that was too big for my happy homeowner drill press.
Unfortunately, I don't think that bb spindles will fit in my drill press. :-(
Your mileage may vary.