I'm guessing that the provisional cast on with waste yarn can be interpreted as casting on with a different color and knitting as usual. When you get to where you need to pick up the stitches, you can put your needle through one loop of the main-yarn stitches and then pull out the yarn that you cast-on with.
ETA--or you can use the crocheted provisional and join after you've worked the first row of main-yarn.
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IngridKH on Ravelry