I had the same issues as you with puckering and just not looking smooth .. until I discovered "stitch and tear" its a stabilizer used behind the applique and tears off clean once you are done with satin stitching. Just pin a square larger than the area you are working in. Do make a small test piece to get the tension and any other adjustments made correct. I am sure you will find your results will be much better.

The same two words keep appearing - starch and stabilizer.