I had a tough time with it too at first. Went through quite a few test pieces. Here's some things that I found: I never could get a good color with Tandy leather, even their high end stuff. It just didn't look right to me. I got good results with Wickett & Craig, Hermann Oak and Chiahin, so I don't mess with the Tandy anymore. That's just me. I have been using Fiebings spirit dye, mostly the British Tan. My customers seem to really like this color. I'll cut it 2 or 3 to 1 with denatured alcohol so I can apply multiple coats if needed. I use sheeps wool to apply all the finishes except the dye.
My process: 1. apply a decent coat of neatsfoot oil, let dry for a day or two. Usually I'm stamping or tooling something, after this It's pretty dry.
2. apply dye, cut 2 or 3 to1 for multiple coats if needed for it to be even. I use the round artists sponges from Hobby Lobby. Buff when dry.
3. If the leather has dried out too much from applying the dye, I might add another coat of neatsfoot.
4. If I have done a stamp or tooling I'll put on a light coat of Tan Kote as a resist (quickly, as it dries fast).
5. Then I will apply either the Eco Flo antique gel or the Fiebings paste. The gel will darken it a bit and bring out your tooling. Buff again to remove solids.
6. Tan Kote again to remove any solids and even up the color.
7. Lastly, a light coat of Wyosheen to protect it. This will give it a subtle shine.
Kieth Valley has a good you tube video of this process.
It's kind of a pain in the neck doing this process but I think you will enjoy the results. I've never done the black dye or the vinagaroon process. I just don't do black. I've tried doing some stuff with the USMC black, it seems the solids come off too easily. I only use it for a border or something like that. Hopefully this helps! It took me quite a while to somewhat figure this out!