Tea tree oil is suppose to be wonderful. Many gypsy vanner owners swear by it, and if you are familiar with the breed, you know they are suppose to have a stocky build and have TONS of hair. MTG works well to sooth and condition the skin, but you're right about not liking to use it ( smells awful IMHO ).
Hot oil is probably another great way to go, but have also heard of using olive oil too. Have you considered either feeding a feed that has extra omegas in it or putting oil high in omegas in the feed ( or a supplement) to treat from the inside out?
The purina senior equine feeds add a great shine to the coat, but purina also sells just the "amplify nuggets" which is a supplement that contains vegetable oils, rice bran and flax seed in a low sugar low starch base. Can be used as a weight gain formula or to help enhance Coat, hooves and muscles. A little calorie dense in my opinion,however, it is a supplement, but I do like the senior feeds even for horses that don't have trouble chewing or keeping weight on, I just don't feed them as much since they get hay too.