There are several ways to baste a quilt--by hand, with safety pins or basting spray. My favorite method is with basting spray which is a temporay adhesive that you spray onto both sides of the batting. I have done the other methods also. If you are using the spray, try to lay out your batting on maybe the dining room table. If it hangs over just spray the middle. Fold your quilt in thirds and lay the middle third of the quilt on the sprayed batting and smooth it out--top of the quilt only. Repeat this step for the other 2 sections of the top and then flip it over and spray the batting on the other side, say 1/3 at a time. Smooth it out too. I should hold everything in palce w/out shifting while you quilt.
A walking foot feeds the quilt under the pressr foot in a more even fashion than a regular presser foot. It keeps the presser foot from pushing the top layer ahead of everything else--it feeds it through like I said more evenly. Is it an option to maybe set up on the dining table to sew? If you think it is heavy now, try wrestling with it once you get your "sandwich" put together of top, batting and backing. Not impossible, I don't want to worry you, but any extra support you can figure out will make it that much easier.
Good LUck :-)