I soak the fabrics in kettles or a sink - Then I spin them out in the washer to get rid of some of the water. I feel that the agitation is what roughs up fabric.
By the way - I have measured hundreds of yards of fabric before and after soaking/washing - SOME LQS fabrics shrink as much or more than SOME of the fabrics I've purchased at WalMart.
A very specific example: A Michael Miller solid black - has shrunk two to three inches in width - and these pieces were from three different bolts.
An RJR very dark navy blue - purchased from the same LQS and treated the same way as the last Michael Miller black - stayed the same size - I think it actually stretched about 1/8 inch.
Another example: A Roc-Lon tea-dyed muslin said "pre-shrunk" on the end of the bolt. That shrunk a lot more than anything else I've measured and washed. It also was "nicer" after being tightened up.
I"m not comfortable using something that shrinks two to three inches with something that does not shrink at all. And I'm not smart enough to be able to tell just by looking at a fabric what it will do.
I also feel that fabric that needs to be treated with Retayne or Synthropol is defective and not finished properly. A bit like buying a car without the protective finish applied.
One of the things I am truly paranoid about is the use of bleach.
But do - or don't do - whatever works for you.
I said I wasn't going to write about this topic again - oops. Couldn't resist.
By the way - I've already seen Scissor Queen's postings that Harriet Hargrave does not think you need to prewash
That does not work for ME or the quilts I make!