Back in May I had the opportunity to attend spring quit market in Salt Lake City. I was a bit overwhelmed but had a blast!! While I was there in the Martingale booth giving a demo, they video taped the technique and it’s now available to see how easy it is.
For the demo I had to make small strips strips but just imagine that sashing strip being 50+inches long. Glue all your sashings and then chain sew all of them at one time. Fast!
Have you tried gluing instead of pinning?