Would love to have the recipe for the homemade basting spray!
I also prefer 505 spray. I do lay down a sheet to catch any over spray from the edges. I tried one other brand years ago and it gummed up my needle.
I've gotten more judicious of how much to spray. I have at times taken several weeks to finish my quilting, without any issues. My favorite way to baste!
I think trying it on a small quilt (or even an oversized quilt sandwich) would help with becoming comfortable and having trust that it really does hold.