I always cut my backing and batting larger than the top. As for brands, I prefer 505 because it is very low odor and very effective (you need little spray) and I also use Sullivan's, although it has a stronger odor.
For my quilts, I put an old sheet on the bed and do my basting there. When done, I press both sides to really set the spray.
Check out Patsy Thompson's youtube on her method of spray basting. She gives a lot of detail.