I myself have only started trying my hand at applique so I don't know if I can be much help. I have not yet tried needle turn although I would like to in the future. Being such a beginner at applique, I like to have my edges already folded under. For larger simple shapes like circles I like to starch after my shape has already been pressed and ready to go just for that extra stiffness and to keep those ironed down seam allowances down. For more complex shapes, I press my seam allowance under. I like to press using a template made out of water color paper. Any heavy card stock would work, even used cut up greeting cards. I have that extra rigid shape to form my fabric around. Seems to help. Once pressed I remove the shape from the template. Then I apply Arlenes Tacky glue, just the barest little bit and glue those seam allowances down. I have found that starching prior to turning makes the turning and ironing process a bit more cooperative, at least for the bigger pieces. Smaller units I do not starch. I have read here Elmers white school glue also works for gluing down those edges. I like the Arlenes because it is very thick (water soluble) so it is easy to just get a tiny little bit on the fabric and it stays put as soon as I finger press it back down.