Leaving the salvages on while washing is a good rule-of-thumb. But if you had the mess I think you had you might want to hand wash the fabric, spin in the dryer and maybe hang outside to dry.
Personally I don't pre-wash. There are reasons why you should, but I have not had any problems. When I had a questionable fabric I would take my 4-cup measure filled with a snip of the fabric and water and boil it for 3-4 minutes. When you take the fabric out and the water has color, it has bled. Otherwise, why remove the properties that prevent mold and keeps a crisp hand?