If you are lucky enough to have a helper, I found this method worth a look. I also was impressed that they didn't spray the back first and then the top. I like how the back is handled by flipping the entire quilt. Not sure ho this would work with a really large quilt, but I have used it for twin size and love the results. I use 505.
https://www.youtube.com/watch?v=dBFAiwmPQBc