I'm also making purses like crazy too. All kinds of charm purses and variations. Teaching people who hardly sew to make them. They are quick and easy and look so cute. Then I made this one the other night...a real Girly Girl purse. :) It's a Tammy Tadd pattern.
Sew about a 5" strip of muslin between the two quilt tops ( I did it on the side that were the same length) and pressed towards the muslin. Then I pieced a back that was big enough to cover both of them. I loaded it on the machine and then proceeded to quilt as usual...except when I came to the muslin part. I quilted along the side of the quilt, being careful not to get into the seam allowances and then only stitched one line across the muslin to the other quilt and then quilted along that quilt's edge. I did this the whole way down the two quilts. When I took it off the machine, I cut down the middle of the muslin and carefully unstitched the muslin (I basted it on, so it was easy to get off) and Voila! Two quilts done in 45 minutes!! I'm not sure if that's how others do it, but it worked for me!