My comments are free... so toss them out if you don't like them. LOL
I wash everything before cutting and sewing, including fat quarters.
I do not do anything to them but toss them into the washer with a few color catchers (which I purchase from Walmart). I have yet to have one bleed onto other fabrics. This includes lights with darks, etc.
Sometimes, and I do stress the word 'sometimes' things are tangled mess. That is why I keep scissors next to my washer. I cut into the tangled mess which releases the mess and then cut the strings at the edge of the fabric before tossing them into the dryer.
Since I am going for the most shrinkage I can get, I wash on hot and dry on hot. I have been doing this for years.