I have only spray basted one quilt, so take my experience with a grain of salt.
If your knees will take it you can use the floor. Lay your backing out and secure it down. Lay your batting on it to get it placed and sized correctly. Start at one end, and roll the batting up to about the halfway point of the quilt. Spray the backing, then carefully unroll your batting. Go to the other side and do the same thing. After that is set, lay your top on the batting and use the same procedure.
I know you can spray baste in sections with your table that is smaller than your quilt. You would start in the center, then work in sections. Hopefully someone with more knowledge will offer more detailed instruction there.
The quilt I did this way is here:
http://www.quiltingboard.com/picture...t-t245620.html
Let us know what you decide, and post your finished pictures!
Darren