That is a great tip. If you have vision problems - not you, Sheena, but Karen - doing that over a light box of some sort also helps.
If the design is photocopyable, you can adapt the quilter's trick. Make a photocopy, then put the copy on top of tissue paper, pinned together. Stitch the design with a sewing machine, but no thread - which will punch tons of tiny holes - perforating the tissue. When using this for a quilting pattern, it's done with a stack of tissue. Then you spray baste, or somehow temporarily affix, the tissue to the fabric, and do the real stitching right over the punched designe. The tissue then just tears right away, and you're left with the permanent stitched in design. I think you could do this with crewel - if you were stitching with wool, I think it would hold up to having the tissue torn away. But, Sheena, you'd know better than I. Or maybe Tia Mary who also does both. I'm not an experienced crewel stitcher. I've also used this way to do the perforated thing, and then pounced the design for transfer.
Or you could scan a design and then print it onto photo transfer paper. I saw a book in the shop yesterday of Russian Punch Needle designs, by Gail Bird. All transfers meant to be ironed on and the ink should last for a few uses.
Just another thought.
ellice