Update on the MTG: Didn't smell quite as bad as I was expecting... Definitely not a good smell, but I was bracing myself after the responses I got. Lol!
I rubbed a small amount into her tail bone (which was drier under the hair than I expected!) and ran my hands down through the hair to detangle it. Let it dry for a while, then braided and put it in a tailbag. First time I've used a tailbag, but I thought it looked pretty good.
Then used a small amount and rubbed into the top of her mane, then ran my fingers through like I did with the tail. Did four french braids like the ones in this vid:
https://www.youtube.com/watch?v=CyPIWYGwvXE (skip to about 3:00)
I know Caly isn't a breed with typically long and luxurious manes/tails, but I'm not showing her anytime soon and she already has decent length and thickness... I want to see just how good we can get it with a little help. Her forelock needs a LOT of help, though. I'm also letting her bridle path grow out to see if I like her having an entirely full mane or not. Would have taken pics but it was getting late tonight and I just wanted to get home. Will try to take some tomorrow when I see how my new handiwork held up!
I will say that I'm already pleased with how shiny and detangled the hair was after I applied the MTG. Time will tell if the dirt sticks to it too badly for me to continue with it.