The baggie thing is not a bad idea.
For a large batch that requires multiple baggies, I always put a date or have sometimes used a random lot number (random, but same number) on each bag.
I recently started using a reloading log, though. I think this is a better solution. Just a notebook on my reloading bench. I use the date for the lot number, followed by a letter, for multiple batches on the same day. I record any pertinent information in there, so I just need to put the date on the physical bag(s) of ammo but will retain a complete , chronological history on file. If you find a problem, you might have to go back further to make sure other lots weren't affected. And when you open a new brick of primers or powder, or make any changes to your dies or setup, or switch to a new lot of casting alloy or a new lube, etc, you can record that in your log and automatically know which lots are prior to, and which are after. When you run into an issue with your reloads, it's like finding a cancer. The less you have to cut away and still be confident in your ammo, the better.
Having had to burn though a carefully stockpiled stash of ammo after running into a bad lot of primers (and they were all good!), and also coming to the realization that reloading is really more of a hobby to me than a cost-saving measure in any practical sense, it doesn't bother me to take a little bit of time to scribble things down in a notebook. It is much less of a bother and inifinitely more useful than carefully labeling each and every container of physical ammo and then tossing that info out after you shoot it.