Are summers family reunion times for you? I learned several crochet stitches from relatives (and in-laws of my relatives) at family reunions. I have a pdf tutorial for the x-stitch too.
My first-cousin-once-removed’s-ex-mother-in-law would use the x-stitch in her fillet crochet – but she used trebles and 3 chains to make her squares, not doubles and 2 chains.