I use Fiebings Harness Blacking, to make the leather black again. Not sure it would not bleed if used on a saddle. Try a ride with some old breeches before you wear the good breeches!
I only black the outside of leather harness, never the insides. Have had bleed off on light color horses, even the dark bays, when sweating up a new harness for a little time.
Sounds awful, but I usually wash new harness with Lexol Leather Cleaner (orange bottle) let it air dry, then condition it, before putting new, black harness on any of our horses. Obviously my harness is a lesser quality than what Thomas would be getting, and my costs are lower than his as well. You have trade-offs with that kind of purchasing.
Sorry, I do not have the time or ambition to hand shoe polish all our leather harness to a mirror finish. There is NO OTHER hired help at this place! Leather is well conditioned, FEELS nice and soft, supple to use, has the harness blacking finish instead. For Presentation, for Pleasure or CDE, Standing or On-The-Move, my method works pretty well. Have always gotten nice scores from the inspectors or Judges.
I have not used the black saddle soap, though David Freedman swears by it in his harness talks. I am not a fan of saddle soap, do not like how it works and feels, attracts dirt. EXTREMELY time consuming to use, clean off, get out of the stitching and crevices. Does not allow blacking to work well. Saddle Soap is not really a soap product at all, but made to add fat to newly made leather coming out of the tanning tubs. Readded the fat to tanned leather allowing flexability again to the hides. The soap name is a trick one, not the truth. Lots of folks love the product, but I do not use it.
I also never use any kind of Neatsfoot Oil or Compounds. The idea of putting that nasty feeling stuff on my harness makes my skin crawl. Leather feels so bad after. Dipping harness in Neatsfoot oil is popular with Draft folks, but actually very hard on the leather itself. Kills the skin cells by making them over-expand with moisture. I never recommend Neatsfoot for ANY leather uses, though again an old method of caring for harness. There just is no comparing nicely conditioned leather to Neatsfooted stuff, when you run your hands over it. Conditioned leather wins easily.
The invention of Lexol Conditioner was one of the hightlights of my horse show career, saving so much time, keeping my leather wonderfully flexible. I now use Harness Honey also, truly a very good conditioner, a step up from the Lexol, not needing several coatings. Does darken light or russet leather though, unlike the Lexol. Both make a pretty water resistant harness when freshly done, doesn’t need any “oiling” of the leather.
I may have a jaundiced viewpoint on harness because of our driving Four most of the time. So our QUANTITY of harness to prepare is large, for any dressy outing. A singles harness would be more easily prepared to show standards, just less of everything!
Someday I will measure how much strap goods we actually have in the Four’s harness, but for now, I REALLY DON’T want to know! I think of it as the cattle-herd-in-a-bag.
I have heard of a new method of boot polishing, using the tins with waxy black shoe polish. You polish the boots, then take the hair dryer or a heat gun, heat the newly polished boots and RUB the polish in. Keep rubbing the warm/hot polish onto the leather boots. Then let the boots and polish cool off, should be no residue because everything has gone into the leather itself. This is supposed to put a mirror finish on, with no rubbing off to leave black smears with sweat or on your saddle. I plan to give it a try on daughter’s boots, see how it works there before trying on any harness goods.