Circular Bind Off

I finally finished the bandana cowl and just need to bind off. The pattern says to bind off very loosely in purl. It says a size 15 needle was used to do this.

I am on circular 9 and do have a 15 straight. I assume binding off in purl is the same as knit but just with purl stitches right?
I have bound off before but only using the other circular needle. To use the size 15 do i just insert it into the first stitch and wrap and go like I would have with the other circular needle?
Thanks for your help!

You are correct: You bind off the “regular” way but using purl stitches rather than knit stitches.

I’ve not used two different size needles to bind off; I wonder if your stitches might be somewhat misshapen (particularly the first two which are just regular purl stitches before you bind them off the needle)?

Can you transfer some of your stitches to the size 15 needle, bind those off using the other size 15 needle, and then transfer more stitches onto the needle until you’ve worked your way around?

There’s probably a better way to do this, but that’s most likely what I would do to ensure that my bind off stays nice and even (well, as nice and even as my bind offs can stay, at any rate).

You’ve got it. Just insert the new needle (size 15) and continue on as if it were the other end of the circular. And right again, binding off in purl is like binding off in knit but you’ll be purling the sts. You might also find htis videohelpful to avoid a bump on the last bind off stitch.
Post a picture of the bandana cowl if you’d like. It’d be fun to see it.

The size 15 is to make sure it’s a loose BO, don’t put the sts from the 9s on them, they won’t fit. Just use the 15 to do the BO, purling the stitches for a ridge on the RS.