I use the glue stick and Rinsaway method for preparing pieces for hand applique.
However, I only glue the seam allowances to the Rinsaway, not the entire applique piece. And I also trim away all of the Rinsaway, except what's in the seam allowance, before appliqueing it to the background. This alleviates the need to wash the piece afterward.
The really wonderful thing about quilting, is once we learn a technique we get to modify it to meet our needs.
Doing applique over a water soluble stabilizer, whether it be by hand or by machine, is a dream. You know how your shapes will turn out before you stitch them to the background. You can really test your fabric choices. AND it's faster. You can make more quilts!
I have to admit, I wash all my invisible machine applique quilt blocks for four reasons:
I'm very liberal with my glue stick. For machine applique, the extra stiffness makes the piece easier to stitch on the very edge. Excess, dried glue stick would make it so much harder to drive the needle through the fold by hand.
I don't like to keep foreign substances in my quilts...I'm going to wash to remove starch and any markings. The Elmer's Glue Stick I use (do you use that one too?) is acid free and safe, but I believe it is a starch product. That could attract critters.
I do like to have the background fabric shrink a bit to hide my stitches. I pretest for fabric bleeding fabric before I start a project...especially for an applique project...so that's another reason for me to wash after the block is finished.
The last block I appliqued, I washed as usual. Guess what I found? Yep, I'd missed a stitching in a couple of places, so I stitched those up quickly by hand. I'd have never found the mistake until the pieces started coming up sometime later.
I would love to have you post some of your work in our online Show and Tell. Please do think about it.