My friend suggested buying Beth Moore's book. I've heard of it but I'm not buying it yet, but the pics on the website look REALLY tempting :) http://fairytale-horses.com/
Some tips helped me:
1) don't brush your horse's mane or tail EVER again. It hurts rather than helps especially on the tail. It pulls out hairs that take a LONG time to regrow.
2) Keep it clean.
3) Condition every time you see your horse (Mane and Tail works great)
4) M-T-G once a week.
6) Trim dead ends
My horse is a TN Walker too, and they have the genetics to grow pretty good, long manes and tails
Here's my boy
(Don't mind the rattyness, he had BAD worms at our old barn)