I too sew the ends together with a zig zag stitch across the end, sure helps with the tangling. Yes it takes a little time to rip out, but if there is fray going on, i just trim off the stitching. I hate tangled fabric.
Pre wash YOU bet I do. I have always prewashed fabric, since I began quilting, didn't much when making garments, depended on the color. Well even with prewashing (before I found out about Retayne and those amazing color catchers), about 5 yrs ago, I made DD a beautiful in my opinion queen size DWR with fabric of cream with specks of green at $12.00 a yard, for inner circle portion and same for the back. I used various shades of greens for the rings. All of the fabric was prewashed, but the first time the quilt was washed one of the greens faded in different places all over the quilt front and back. The quilt was Air dryed, and washed 3-4 times using everything I heard about to get the green spots out, but to no avail, they are still there. It has never been in a dryer. Greens seem to be really bad to bleed. You won't catch me not prewashing all of my fabrics after that incident. I was working when I made her quilt, and it took me about a year and a half to complete it. Too much time and expense spent, only to have it ruined in my opinion. I even prewash fabrics no matter the color that I have never had a problem with bleeding and am almost postive they won't bleed, but just not chancing it, rather spend a little time before all my work, than be devestated from a ruined quilt later.