I don't wash my fabric first. However, when I want to starch a lot of yardage, I mix up a solution of Sta-Flo liquid laundry starch and water. I "paint" this solution onto the yardage with a large wall painting brush until the yardage is saturated. Toss in dryer, iron with steam. This is the fastest, easiest way I have found to starch large pieces of fabric. (My hand would get very tired trying to spray starch on a lot of fabric!!)
If I want to prepare a quilt top for layering, I just use a commercial spray starch and try to be *very* careful about overspray and iron temperature.