I spray baste my quilts on my king size bed covered with a big flannel sheet. The flannel keeps everything from slipping around. I put the batting down, position the backing over, fold batting back half way, spray the batting and smooth the backing down. Repeat for the other half, flip everything over, position the quilt top and repeat the whole process. I mostly use June Taylor, but have used Sullivans and 505. Spray very sparingly. I have found that some fabrics take to the spray better than others but it's best to spray lightly until you find out if you need more or not. With practice you can baste a big king size quilt in under an hour. Here's a link to one I posted a while back.
http://www.quiltingboard.com/t-87591-1.htm