I wash my fabric and then rip it into strips that I then cut into patches or sometimes cut at the muzzle.
Before washing your fabric, use a sewing machine to sew around the cut edges to prevent raveling. If you don't do this, the fabric will ravel in the washing machine and get all tangled up. If you don't have a sewing machine or don't want to bother with sewing around the cut edges, you can put the fabric into a mesh bag or an old pair of panty hose when you wash it. Of course, you can always just wash it by hand. After washing the fabric, it will be pretty wrinkled so I run an iron over it to smooth it out. Is it necessary? I don't know :idunno: .....maybe I'm just anal but it what I do.