Pick an empty that is a style you prefer. Some have narrower mouths than others, and some are flat and narrow rather than cylindrical. Just find a shape you are comfortable with and that you can control well pouring into the powder measure. Fill it only halfway. Label it something like "powder name - working stock". You can print it on a sheet of the peel-off, stick-on labels and put one on your measure when that is what is in it. You can also return powder to it (this is why God made funnels) if you have to change out what is in your measure, though I would get in the habit of leaving the container as the only powder container on the bench until that is done. Otherwise, you increase the chances of accidentally mingling two powders. Never pour anything back into your 8 lb jug. If you realize (you should always look at powder when you pour it out, as an added check) that you've mixed two powders, you then have only a partial container of orphaned powder rather than being faced with the nightmare of trying to segregate an intruder from your larger store.