I like the 505 best because it's acid-free and will hold indefinitely. I may be mistaken, but I don't think the Sullivan's is acid-free. The Sulky spray is designed to release after a couple of weeks. I take so long to quilt a quilt that I'd find this most frustrating. Neither the 505 nor the Sulky spray gums up the needle, in my experience.
I smooth out my quilt backing on a table or carpet. I tape it down if it's on a table, but not if it's on a carpet, because it sticks to the carpet and doesn't really move.
Then I lay the batting on top of the backing.
Once the batting is smooth, I fold half of it back and spray about 12 inches of the backing. I carefully lay the batting down and smooth it out again. If I get a wrinkle in it, I peel it up and carefully lay it down again. It seems to help to settle the batting onto the backing from above, rather than dragging it across the sprayed surface.
Then I lift the batting again, spray another 12 inches of backing, carefully lay the batting down again, smooth it out again, and so on.
When I've done the first half of the batting, I do the second half, again working from the centre to the end of the quilt.
Once the backing is in place, I repeat the whole performance with the quilt top. If it's a large quilt, when I'm done I insert safety pens every six inches or so. Don't know if I need them, but I'd rather be safe than sorry.
The overspray is a pain to try to clean up, so I always put a piece of newspaper or cardboard under the edges of whatever I'm spraying. When I do get it on a table, I can't get it off with anything other than the DK5 spray that's made especially to remove basting spray from hard surfaces. Not even nail polish remover seems to touch it.
Anne in Vancouver, Canada, a confirmed spray baster