Like Genden stated it would depend on how ( wonky) your quilt is which method would be best. I've always managed to trim as I go, keep everything square, then I trim & square up after quilting before binding. I haven't had to block any quilts other than a small wall hanging that really ( wonked) on me one time...that one I misted with a spray bottle but had to really saturate it to pull it into shape. Took 4 days to dry. Learned lots from that one & don't make those mistakes any more.