I use the Gum trag for edging but you have to use it after you dye the item or the edges won't take the dye as well, I second the fiebings suggestion. I use the Super Sheen or Acrylic Resolene on most things
I have never used the Neatsfoot oil prior to dyeing an item. I would try it on a scrap first.....
Also to get a more even finish make sure you use the largest aplicator you can find or spray it.
This is Fiebings USMC black with a double cost of Super sheen.