Yes, try the extra support with an ironing board or table to the left of your machine. The whole quilt should be on a table, none should be hanging over the edge.
When I first got my walking foot, my dealer told me to make sure that you have a little hump of extra fabric in front of the needle. The fabric shouldn't just be flat on the infeed, the little hump or pleat means that you're not pulling on the fabric and it lets the walking foot actually feed properly. As you sew, you keep gently pushing the fabric forward to maintain that little hump, guiding it into the foot. I just used my walking foot to attach a binding, and used this method. Quilt feed very smoothly. Oh, and i always have a quilting glove on my left hand to guide the fabric and move it forward.