You should be able to remove all the metal parts unless they are rivetted on. Even then, you can still use the washer. I use a LOT of Woolite, and then a LOT of fabric softener, and lay flat to dry. Be sure to brush the nap down while they are wet. When the chaps are almost dry, I will wear them around the house for a little bit to kind of stretch them back out and fit them to my legs. The very last part is tossing them in the dryer for a few minutes on low heat to soften them up.
I've washed pretty much every pair of chaps I've owned, and even dyed a few :)