Nicole, I wash my neoprene girth and reins, and biothane bridle and stirrup leathers, and anything nylon (halter, example) in the washing machine on COLD, AND DO NOT DRY. Hang them to dry. So easy! Just throw them all in an old pillowcase or two and tie closed before you wash them to keep the buckles from clanging too much, keep the reins/girths from wrapping around things, and to keep the inevitable horsehair from clogging your washer!
...you will be more disappointed by the things you didn’t do than by the ones you did do. ... Explore. Dream. Discover.”