Hi,
I use the straw needles #11, and I also use the needles that are labeled Applique in different sizes, depending on the thickness of the fabric. Some brands go through several layers better than others. You need to try a few different stlyes to find what you like the best.
Invisafil thread works even better than silk. It comes in many colors and even though the piece may be dark, an off-white thread is almost invisible. To find a source, just enter Invisafil thread in your browser. I only know of one quilt shop online that carries a wide variety of colors in this thread at this time.
I have been doing needle-turn applique for about 20+ years.
Good luck!