I've never heard of this method, but it sounds interesting.
Lactic Acid Bacteria, which is what IMO3 (indigenous microorganisms) is, is easy to culture. Cabbage is naturally covered in Lactic Acid Bacteria. Look up how to make sauerkraut. You can use the excess liquid from that to make your starter culture to use in
this method.
Any add all grain/seeds are good for
chickens and chicks.
Chickens can take things up to corn kernel size but chicks need something smaller. Naturally, the mother hen will pick out food the right size for her chicks. If you are not letting the hen feed her chicks, then I'd stick with chick starter feed until they are a bit older. Sprouted grains are much easier to swallow. You could try a sprouting mix such as
this if you want but keep in mind that chicks need lots of protein, so I'd be careful about limiting their diet.
I give my chickens all the weeds I pull from my beds. They eat what they want and shred the rest into the coop floor. After a few days old, chicks can eat small greens too, but you have to be careful that they are small
enough for them to swallow. They aren't able to shred their own green yet and a long piece of grass could get stuck in them and they could choke. Make sure anything you give them is no more than 1/2 inch long.
As far as feed mixtures, I'd let the birds start foraging as soon as they can. Then all you have to do is worry about macro nutrients (17%-20% protein). But if you really want to, make sure that there is a wide variety of seeds and grains from different families of plants.