will work if you use a poly blanket as batting? I like using blankets on the kids quilts as they are heavier than batting and I thought I might try my hand at spray basting today.....but I'm wondering if the blanket will be too heavy?

Maybe I was doing it wrong, but whenever I have spray basted with a poly batting, I always end up with wrinkles on the back. It was frustrating because I kept fighting with the stickiness of the spray to straighten it out.
As far as it being too heavy, I don't know.

I used spray basting on a poly-cotton backing one time. The batting in between stayed sticky but the backing kept falling off. I ended up having to pin the backing on. Don't know if that helps but that's my experience with polyester and spray basting.

I have done it before with a fleece blanket and had no problems. My back came out smooth.

Try it on a small part and see what happens.

One thing I have found is that you need to follow the directions on the can when it says to use at XX temperature. If the spray is too cold, it doesn't adhere as well.