Karen, you say (I´m not sure I can do a provisional cast-on, but after watching the video here on KH, I can tell you that you can use a spare circular needle instead of waste yarn and then knit right off of that. Does that make more sense?
Sorry, that I must be dense. I can follow using the crochet hook casting on over the knitting needle, but this is with the waste yarn. the tip says to use another circular needle. I can't seem to picture where this other needle would be. You say use the circular needle instead of waste yarn, but the waste yarn is what is used to cast on with, not sure how you would use a needle instead.