I use Sullivan's and I love it. However I do have three big tables I put together to lay my layers down on. I have heard but am unsure if it's true but people have said it doesn't work as well on a poly/cotton batt. If you were having success with applying it to the fabric then to the batting then I would do it that way. Taping it taut to the wall would help also. I can spray baste anywhere from 5-6 oversized twins with one can. You don't need a lot and it will hold for quite a long time. Just be careful and don't overspray. Also doing it in sections helps a lot. I'm not sure how large of a quilt you're doing but you could you lay it down on the kitchen floor or even a room with an area you could lay it down on...that might help you. I used to do this before but got tables at Costco as my knees couldn't squat/bend like that anymore.
I know you're in a rush but try to find some special deals on the spray online or where you live if possible.