I hand quilt with the rocking motion. One thing I learned early on is that it is important that the quilt NOT be drum tight in the hoop. You want to be able to move it about a fist-size up or down in the middle. This slackness allows you to manipulate the fabric, not just the needle. The second thing that really helped me was finding the right thimble. For me, the thimble MUST have a pronounced raised ridge around the top to hold the needle while I am rocking. If you look closely, most thimbles are made for hand sewing, and they have a rounded top. The rounded top works fine for hand sewing, but it lets the needle slip when you are quilting. Also, most sewing thimbles have pretty shallow dimples. It helps to have a thimble with deep dimples, both on the sides and inside the ridged top. Those deep dimples hold the needle better. I will attach some photos that show the type of thimble that work for my rocking stitch. The second website also lists the brands of each thimble:
http://sentimentalstitches.net/instr...hand-quilting/
http://academyofquilting.com/class-s.../?classesID=50
The above doesn't work if you have long fingernails but if, like me, you are used to short nails it will be fine! It is also important that the thimble fit your finger. If a thimble is a little too big, you can place a small amount of children's clay inside to help it stay in place. Once you determine which finger works best for the thimble (with the shape of my hand, the middle finger works best for me), you still might want to get two sizes of the same thimble since fingers can swell a little in heat.
I will say that one of the best award winning quilters in my old city owned a quilt shop, and she quilted with the "stab" method. That is, she stabbed the needle down from the top, grabbed the needle underneath to pull the thread through, then sent the needle straight up with the underneath hand. She said she could never get the hang of rocking. I simply don't have that kind of dedication. My rocking stitches are not as perfect as her stab stitches, but I would not have the patience to make two hand motions for every single stitch!