If I know I'm going to flip blocks around after they're finished to play with the design, I typically just finger press seams. Like on a drunkards path quilt. Then when design complete, I press the seams for nesting. If I can't do that, then I've been known to repress blocks or just press seams open, too. I don't like the bulk but, obviously, this can't be avoided sometimes. Eleonor Burns teaches a neat twist technique but I've never been able to do this. She does it on pinwheels but I just press pinwheel blocks open now.