Update: my grinder died mid pour over on Christmas morning and I had to get creative
There I was at 7am on Christmas at my sister's place in Boise, and her old blade grinder just stopped spinning halfway through a batch for six people. I ended up putting the beans in a zip bag and smashing them with the bottom of a cocktail shaker, which gave me the most uneven grind I've ever seen. The pour over took forever to drain, like 7 minutes, and the cup was muddy but honestly still drinkable. I'm now looking at hand grinders for travel so this never happens again. What's everyone keeping around as a backup when their main grinder quits on a holiday?
Brought my hand grinder on a camping trip last summer and felt like a genius until I realized I left the handle at home. Spent 20 minutes crushing beans with a rock on a flat piece of slate, which honestly is not that far off from your cocktail shaker method. The muddiest cup I ever made, but when you're sitting by a fire at 6am you'll drink just about anything. Now the handle lives taped to the grinder body so I can't pull that stunt twice. Your sister got lucky you didn't just serve everyone instant and call it a Christmas miracle.