An absolutely gorgeous job you did on this and I love how you figured out to use samples and put them into a gorgeous quilt. One thing I will say about spray baste, as I use it all the time and don't use it outdoors...it's fast, very efficient and if used carefully there is no over spraying. Since I use hairspray in greater quantities that spray baste, I'm not too worried about the occasional quilt. Just finished one that I had lightly basted and half quilted, folded up, pushed into a basket, manhandeld and took out again to work on...the baste held beautifully...no pins in it ever btw.
What I AM very pleased to see was you use of warm water to thin the glue...that was very smart and something I'll try in the future. But spray basting, for me is the only way to go. One must be careful, take your time and do the lightest of applications...it holds and can be adjusted in the case of wrinkles, and not need to be resprayed.. for edges, push the quilt to the middle of the table and spray there...if there is any overspray it will go onto the table to be cleaned up. Once again, beautiful job on your quilt.