I learned from You Tube videos. Your bag could be done magic loop or another in-the-round method using one or two circulars and use the same needle(s) start to finish I expect. If you share a link to the pattern we could tell you for sure if that's possible.
When I decided to learn to knit in the round I tried dpn and got frustrated; if I'd had bamboo dpn it might have worked out better but mine were aluminum. I learned magic loop instead. I use the same set of needles start to finish on hats and socks - socks I knit toe up, two at a time. I have, since those first attempts, used dpn and will again but my preferred method for small circumference knitting is magic loop. There is also traveling loop which can use a shorter needle than required for magic loop and some people absolutely love using two circs. I like one long circ because when I use dpn I am always and forever dropping and retrieving the empty needle which finds all kinds of ways to hide but circs are leashed and much easier to retrieve. When I use two circs I do fine until I get distracted a bit and use one needle for all the stitches and end up with one empty needle.
Dpn for me has too many moving parts and pointy ends. YMMV as it does for many other knitters. Just find what works for you.