use caution when using horse clothing laundry services. i have found that many of them just shove the blankets in a washer and destroy the waterproofing. and generally once the waterproffing is gone you cant replace it.
my solution has been to hang the blanket/sheets on a fence and use a hose with regular nozzle and spray them down with just water.
for the blankets that are really dirty get a scrub brush and scrub away.
Find friend with maytag neptune or buy one yourself, it works for king size comforters and big dog beds and giant heavy rambo turnouts (or a similar washing machine with no ringer).
Use cheap human shampoo (I use the tresemme, regular type).
The maytag even holds the heavy weight rambo wug plus with attached neck rug.
Water repellency remains after 3 or 4 years of use.
I did this once and ruined the blanket. Don't do it!
Hand scrape any caked manure or mud first at home, then launder in the machine. Make sure you use laundry SOAP (very tiny amount) and not detergent, as the detergent supposedly gets into the 'pores' of the ballistic nylon and makes it breathe less.
Only launder your rambos when you absolutely must. I field wash them as much as posible and only launder every couple of years. They last must longer.
I love Rambos --- I have one that's 15 years old and has been used every winter and has only been sprayed with waterproofing once!
I have used a pressure washer many times on gross blankets. The lowest pressure setting also sprays the soap on, then I just turn the pressure up a little bit at a time until I like the way it cleans and have at it.... Then I move to the trailer
I also stick them in my Duett to clean.. It all depends on how gross.
I've done this. Doesn't work very well. You can't have the pressure up high enough to really get the dirt off or you'll bore holes through the fabric. On a lower setting it only gets a small amount of the dirt. I think a scrub brush and a hose works just as well.
I use the waterproofing spray stuff from WalMart to re-waterproof.