Personally I have never found stab stitching to work very well.
As to the usual "rocking" method, it does take a lot of practice, and you are doing right in using a small piece to get the hang of it.
How well is your quilt basted? The layers will shift even in the hoop if it's not basted enough - I always think that "more is more" when it comes to basting and I probably overdo it but I think it helps.
Are you using a good thimble? If not, use one, you will soon get used to it.
Try quilting in different directions - by which I mean not only horizontally from right to left, but vertically top to bottom (my favorite), and even bottom to top, pushing the needle with your thumb (you will probably need a bigger thimble for this, using the side of your thumb).
As you are finding out, theory and practice can be two very different things - keep at it, and it will come. I still need to have a small piece to make a few needlefuls on before I move to the "real thing" to get my hand working properly each time I begin a quilting session.