Wow! Lots of comments about spray adhesive. I will direct you to Film on the Fridge's blog - I used her tutorial and it worked really really well. And I will answer your questions here too:
Did you purchase a specific kind? Yes! As per Film on the Fridge I bought 505 temporary fabric adhesive. I found it at Walmart. I thought it was quite expensive, but it is so very worth it!
Did you do yours outside? On a patio or something? If inside, did you have a problem with the spray getting on the floor around the edges of the quilt?
I laid my quilt out on the hardwood floor in my kitchen. I did tape the batting to the floor so it wouldn't slide around. Ashley wears a mask when she sprays - but I didn't. I hardly noticed any fumes at all. (It's probaly safer to wear a mask though). About the floor - there was a little bit of film from the spray - but it washed off really easily with a damp cloth. The other thing about spray adhesive -- follow her instructions about how much to spray! The first time I got frustrated and sprayed the entire half I was working on -- that didn't work as well as spraying a foot and spreading out the fabric and then spraying another foot and so on. I found starting in the middle and working my way out really really helpful for getting all the wrinkles out too.
I'm a convert that's all I have to say ... no more pins for me! Happy spraying!