Tarpan, I'm not sure how readily available it is in the US, I know that a few of the Aussie suppliers do ship there though, but see if you can get your hands on some 'Hi-Shine' oil. It is FANTASTIC!!! You use it as a hot oil treatment, so put some in a bucket of warm water, sponge liberally over the horse, shammy off the excess water then put an old blanket over the top. It will soak right into the hair and skin, and makes the hair increadibly soft and shiny, and he skin is so much healthier.
My gelding had a god awful coat through winter after being clipped and having living out in a paddock for 12 months. I had a Dressage Championship event on last weekend and he was still holding onto quite a bit of the awful dry, yellow fuzz. Gave him a good once over with Hi-Shine two days before, and he looked a million dollars for the comp.
Also use it on my 2 year olds tail, who tends to get a lot of dandruff - Hi Shine has cleared it up completely and his tail is beautiful. Best bit is that it actually encourages the coat to repel dirt, and it doesn't 'coat' the hair like all of the sillicon based detanglers.
Great stuff, I'd highly recommend it.