I use detangler in my guy's manes and tails quite often. The human stuff is a lot cheaper than the fancy horse stuff and it works just as well. :)
I don't know where you live or what the temperature is there, but I personally wouldn't wash a horse in weather under 60 degrees F, especially without a cooler or warm area to put them afterwards. Why not try a sponge bath? I've heard vinegar in a spray bottle can work well to clean dirty manes and tails when bathing isn't practical.
I think that most of those products should be okay...
Paul Mitchell actually makes pet shampoo and wipes and such that are awesome, but its only cheap if you have a cosmetology license..which I do. Otherwise the retail price is a hole in your pocket. :/
I've been diluting a leave in conditioner with water in a spray bottle and it's worked pretty well!