what I do...
If the hair looks kinda matted and bunchy at the ends, this is what I do:
Wash the pony's hair and then put a TON of conditioner in it. Take the hair into small sections (maybe 10 sections for the whole mane) and use a very fine tooth comb to comb it through. If the hair is really matted, you might try a wider comb at first. Now, alot of loose hairs will comb out into the comb, but dont worry, because when she dries she will be great looking.
Once I comb through the whole main and tail like this, I rinse it all out and then just put in a normal amount of conditioner and let her dry.
You can be pretty rough with their hair and not mess it up, at least in my experience,
~Lisa~