Mixing of powders to make stock solutions For a solution such as:

Luria-Bertani (LB) Broth:

10 g tryptone
5 g yeast extract
10 g of NaCl ($M = 58.44\ \mathrm{g/mol}$)

q.s. to 1 l, pH to 7.2, autoclave.

I would like to make a bulk amount of premixed powder, i.e. combine 1 kg tryptone, 500 g yeast extract and 1 kg NaCl in a big bottle, shake it and keep it on shelf. Whenever I need to make LB now I just weight 25 g of this premix and add to 1 l of water.

I’m concerned about a couple things thought. First how thoroughly it gets mixed, and second any settling of different chemicals over time. Either would cause many different batches to be messed up. 

I’m wondering if anyone has experience with this and ways to avoid those two problems. I’m interested in doing this for other solutions as well. Do manufacturers who make these premixed powders re pulverize them or process them in a certain way to make it work?
Once the powders are mixed, it is unlikely that they will separate unless the container is subjected to vibrations.

As for mixing, companies that need to mix batches of material use a mixer to make their batches. The second photo in the article is similar to what I have seen.