I think I may have found the quilter who gave classes on how to use ugly fabrics. Here's her website:
http://www.quiltsbylyn.com/index.htm
Also found this description of her class on a retreat website:
"Some of the concepts we learned in this class are:
Value--make sure there's a contrast in value between the ugly and the pretty fabric
Texture--make sure there's a contrast in texture (this is maybe why a quilt made of nothing but Moda marbles can be pretty boring)
Scale--there also needs to be contrast in scale, pair a big print with a much smaller print
Pull the lesser of the colors--for instance, if the ugly has lots of muddy browns & oranges and just a touch of yellow, try putting yellow with it to make it look prettier
Stand back to observe--this lets you ignore the little details and concentrate on the contrasts
Without contrast there is no pattern--you can cut and piece until you're blue, but it will all look like one fabric
Cutting smaller pieces will blend the fabrics better
Color is not the most important aspect of pairing fabrics
There really IS no such thing as an ugly fabric--virtually any fabric can be paired with another that will make it look better "
Unfortunately, I never took her class and apparently she didn't write a book about how to combine fabrics. Sigh.