Where do you pin baste? Is it on a table? On the floor? How close together do you pin? Do you have any pictures you can post?
When I baste my quilts I do it on my cutting table and i use the spray glue and pins. (I do both if I am not sure how quickly it will be quilted). But my table is my cutting table and about 6 feet long and 30 inches wide. So I baste it in sections. Also, it goes so much better if I have help, but that isn't always the case, it is just easier. (I do wear a face mask when I spray.) It really is the glue that keeps it from puckering for me.