Another thing you can do. If you have quilt magazines you don't use any more...find one with a tutorial on how to do the borders, or whatever is wrong with the customer's quilt. Gift them the magazine...."I am finished with this magazine, it's got lots of good helps for doing borders (flying geese, half square tris, etc.)." I do this with mailed in quilt tops and now with those coming into the shop...just subtle hints. Also, if I have the customer in front of me...I'll show what I had to do to make the borders fit...and then if they ask how to avoid the fullness...I will explain the process to them (and lately I give out how to sheets). Free lesson for them, less headaches (we hope) for us on the next quilt.
Marge