JT, its been over a decade since I was in the leather business, so I don’t have current sources and I probably am off a bit on names. We had 1 machine set up for sewing natural undyed leather, in it we ran Barbour linen thread, left hand twist, I think, and used Sellari's stitching wax which had to be heated. The other one was set up for sewing black dyed leather, I know it took a fair bit of experimentation to find a synthetic that would work, some were so stretchy it really messed up the machines timing or just didn’t give nice looking stitches. We used some type of liquid wax with that also, but I think it was different than the Sellari’s. Check with the folks at SHATA that I posted in the other link, or the International Internet Leathercrafters' Guild at IILG.org or probably best a local saddle maker.
Todd
