no - I just squirt it in, but I don't measure the regular soap either. I like to go light on soap, I bet I add about 1/8th of a cup.
I've not had problems with die setting on fabric I'm prewashing that I use Dawn and color catchers. however I have had some bleeding when washing quilts after the are finished, and then I use regular soap and color catchers. Maybe I should switch to washing completed quilts with Dawn instead of regular detergent. So far it was one specific red that did this on two scrappy quilts.