How to cast off purlwise

Is it purl, purl, slip *purl, slip ?

And is casting off on double pointed needles the same as on straight needles?

Check out the Basic Techniques “Binding Off” section for tons of videos on casting off.

Yes, casting off on DPN’s is exactly the same.

How do I finish this off? There’s 1 stitch left on each of the three DPNs.

You start at one point and continue all the way around just like flat… you don’t start casting off at three separate points along the row, whether knitting flat or ITR. If you can undo the castoff and start over again all in one piece do so… but if the thought scares you, you could actually weave in all the ends separately.

When casting off in the round, you’ll get a perfect join if the first stitch you cast off gets put on the last needle and becomes the new last stitch.

How do I weave in the other 2 stitches that don’t have any yarn attatched?

You can take a bit of yarn and tie them off, or undo the whole cast off back to the first stitch you skipped and cast them all off. When you work on dpns, you cast off all stitches all the way around; when you come to the one on the end of a needle, you purl the first one on the next needle and slip the end st over it. It doesn’t matter that they were on different needles to begin with.