I glue baste with washable school glue (Elmer's or whatever) and never iron. I just let the glue dry naturally. I hold the bottle about 6-8" from the quilt bat and let it come out in a fine stream and do a zigzag pattern then smooth the backing or front over depending on which side I'm working on. I've never used an iron and never had any problems. Overnight is a good rule of thumb for dry but I'm sure it's probably dry before then.