Steve,
You may want to take a look at this link; http://www.youtube.com/watch?v=f24kj03oEmo it may give you some ideas as to how to build up your cushions, etc. This is pretty much the way automotive upholstery is done. While having a walking foot sewing machine is great the same thing can be done with an old garage sale Singer if you adjust the foam and fabric thickness.
kebo