I asked a similar question because some overspray got on my acrylic sewing table. It's supposed to be water soluble ... I can't get off the table.

(1) I personally don't think it matters, but it's usually advised to spray the batting.
(2) Small quilts get done on the kitchen island. Large quilts on the floor, but I would like to use a wall some day. Have read posts from people who have used a garage wall or a garage door.
(3) I lay out sheets to cover an area much larger than my quilt. Usually a king-size flat sheet is enough. Spray from the edge towards the center to minimize overspray. I like sheets because they can be tossed in the laundry.

I have never had an overspray problem but if I did, and if it did not come off as expected, I would call the manufacturer and ask their advice.

I also use the 505 spray but do tape my backing down to the floor (or other large hard surface) before spraying and sandwiching which cuts down on any wrinkles on the backing.

I have seen a lot of questions about over spray and I have only one suggestion to all of you. Try Simple Green. It will remove the built up greasy road film from the fenders of my car here in Alaska where nothing else would and it is biodegradable and non toxic. On the tough stuff I used it full strength. Hope this helps.

I wonder if goo gone will work?

Sometimes for guey sticker/lables and sticky things, I use lighter fluid and it works great and doesn't destroy anything. Perhaps giving that a try will work

W-D 40 or Antibacterial hand sanitizer might work. I use the hand sanitizer for everything sticky.

I tried goo gone and it did not do as well as Simple Green. But hey, anything is worth a try. You never know depending on the area that needs cleaning and what it is made of.

Ok I just tried my first spray basting. Was thrilled with it, said I will never use a pin again. ... Then I turned it over and realized that the baking had come off and was not glued to the batting and I was all puckered in the back.UHHHH what to do.... Learned a lesson though. Always start in the middle and work out but since others had said that the sides are what come apart I decided to do around the edges. Well, I fixed it and finished it. I think that it came out OK, will post pics tomorrow.

I use Goo Gone and it worked great!