When I machine appliquéd The Magical Unicorn, I turned under and glued the seam allowances in place. I didn't have these dandy tools when I made my own quilts, but they would have made the job of manipulating the seam allowances a lot easier.
Olga Rosa, who lives in Spain, developed the Apliquick Rods and she produced the video below which shows you how to use the tools.
FYI: Ms. Rosa prepares a fusible shape for each appliqué piece from a paper that mostly washes out. You fuse the shape to the wrong side of the appliqué, trim it out leaving a 3/16" seam allowance, and then you glue to the fusible.
I don't want to have the residue of the fusible paper under my appliqué so I make freezer paper templates and iron them to the right side of the cloth. I turn the seam allowance to the back of the fabric, following the edge of the freezer paper. I remove the freezer paper once the shape is prepared and proceed with my machine appliqué.