I agree with addressing the fence issue first off. And I know MTG is greasy (smells yummy!), but it works. If you're interested in going an all natural route, here's what I do. I feed my horses flax seed and canola oil in small amounts once daily, wash their manes and tails with a dandruff shampoo mixed with fish-oil and other vitamins, after that's done I condition with olive oil. Olive oil does attract dirt, you can use Coconut oil as well. IF you do go with olive oil, brush carefully, braid and wrap or bag the horses mane/tail once to twice weekly. I've noticed a huge difference in my horses hair, shiny, silkier, longer and moisturized!
PS. Only brush your horse's mane/tail when you rebraid/wrap. Also try to use a paddle brush, I highly recommend the Oster Mane and Tail brush! My horse misplaced mine, so I'm buying a new set.