This is a really excellent thread! Extremely informative.
I use Stay-Flo at a 1:1 ratio. I use a clear spray bottle purchased from a Home Depot type store because it's a clear bottle meant for mixtures of peroxide. It doesn't clog up the sprayer like it does some of the cheaper sprayers. I do not prewash my fabrics if I can help it, the only exception is flannel.
I have a chart somewhere of bed sizes vs quilt sizes and the sizes mentioned so far is what works. I'd rather my quilts be too big than too small. Wrinkles wise, I find clothes behave the same way as fabrics. I have some of my son's slacks that have to be pulled out of the dryer before dry so they can hang the rest of the way and prevent wrinkles. My ironing surface is just a pad since I don't have an ironing board. It's horrible enough when I have to press long seams, I certainly don't have the ability to press big yardages out. I too fold my fabric differently every time I get some out.