This is like, the latest reply. But ugh they're so beautiful! Love that you just jumped in at the deep end, especially with that non-standard cufff. The darning took me a second to spot, too. Need to try that for the first time myself soon and I'm dreading it so if you have any protips I'm all ears! 😬
Darning is where my yarn hoarding paid off; I still had some of the original yarn left over.
There are a variety of tools out there. The darning egg and darning mushroom are two variations on the same principle: stretch the material slightly while stitching so the mended area stretches with the rest. I had a darning egg that I found at a thrift store years ago and used that. I think a mushroom would be handy for larger areas or objects. There is a darning/mending loom that you can set up on the item and that will help you keep your stitches neat and even. I don't have one but I definitely see the appeal.
I think knowing the sock was already damaged and I couldn't make it worse helped to steal steel my nerves. I wasn't going to ruin the sock, it was a hail Mary attempt to save it. It was my "gateway drug" into mending. Since doing that, I have now used sashiko stitching to mend two pairs of jeans and have a few other things that I plan to mend.
Thanks for this! I also have some of the original yarn, which is nice because it's a really weird specific blend of all sorts of fibres including bamboo and silk. They were also my first socks and as such have been worn to death and have an extremely special place in my heart. Hopefully I can post a darning success of my own soon!