I'd never used glue until I went to a demonstration at one of the national quilt shows. That experience changed by quilting life. I use Elmer's school glue and only the school glue. It's the washable one. I use it full strength and have a bottle with a very thin tube to apply it. I apply the glue to the seam allowance but never on the seam itself so I'm not really sewing through the glue. That fine tube really helps with that.
I always heat set the glue and if I lined things up wrong, I can pull it apart and reglue it. I've never had a problem with it being lumpy or hard. Mitered corners always match perfectly now. Stripes are easy to match and any seam that has to fit perfectly always does.