My horse's pasture mate tore out chunks of his tail, so I've been using MTG for about a month. Here's some tips I've learned:
Don't apply it every day! I did this at first (oops!) until others on this forum told me to only apply it weekly. After I starting applying weekly, I noticed new hair growth in about 1 week.
Dirt + MTG = Goo. Yeah, after a while, the MTG and dirt (my mostly white Paint rolls a lot too!) will kind of build-up in the hair. I've just been brushing it out, but there's still some residue. We had one hot, sunny day, so I gave him a full rear-end wash and then re-started the MTG treatment.
Since it sounds like you're going for length, I would also recommend to braid/tail bag it or do AKPaintLover/Appylover's trick with the Vetwrap!
Also, I find that I wash my hands really well, immediately after applying the MTG, the smell comes off my hands well enough to not smell like Bacon on a BBQ all day!