I don't know if the suggestion has already been made (I did not read the entire thread) but the aerosol hair oil spray for colored women called Pink works wonders on the mane and tail. But it's ONLY the aerosol that works so well, I don't know why the other oils don't.
It can be a little slick, so I would not recommend it within 24 hours of braiding, but it over time makes for a shiny, moisturized mane and tail. Jack's got a THICK, wavy tail and this stuff is a blessing.
Cinnamon Whiskey 11 y/o 15hh Chestnut AQHA mare, 2'6 Jumpers