I think you will find this
video helpful. He first goes through the traditional way to use pins to line up points (which is *very* helpful if you have not already found this technique), but then show his way of using dental floss to keep the points exactly lined up through the stitching process. The same person also has a
second video that has a bunch of tips that will help with pin wheel piecing and getting all those diagonals to be just right.