I just finished my first large free motion quilting project. Before this, I had done quite a few smaller practice pieces, and frankly didn't get the hoopla about using some sort of friction reducing product under the quilt. It wasn't really necessary on smaller pieces, but once I stuffed that quilt under the harp and tried to move the quilt around with my two hands, I truly understood the need!
Since I didn't want to wait for an online order to come in, I found the youtube video where Marguerite demonstrates how to build up her easy quilting table. She uses the clear vinyl table covering material you can buy at your local Wal-Mart, Hancock Fabrics, or Jo-Ann's. I used her instructions to build my folding table up to the bed of my vintage Singer 15-91, then covered the whole surface of table and sewing machine bed with the clear vinyl. It worked just fine to reduce the friction, but I got frustrated with bobbin changes-- I had to remove everything to access the bobbin case. Depending on your bobbin access, you might have to similarly remove the quilt and move the slider out of the way each time you needed to change bobbins.
My other machine, an older Bernina, has a custom insert so it sits flush with the sewing table surface. The table top is made of slippery Formica. My machine is a vintage metal one, so I used Johnson paste wax to buff the machine bed and table. It worked just as well as the vinyl to reduce the friction, nothing else was needed. My hands are small enough to reach under the insert from underneath and change the bobbin without having to remove my quilt. So I switched over to the Bernina for FMQ.
Oh, and just like everyone says, the quilting gloves really help with moving the quilt around, too.