Most of the colors you will only need 1 can, bottle, or tin..whichever they come in. the only color you may need 2 would be the Model master panzer oluvgrun as that is used for the main green. Everything else, 1 is fine. Humbrols are in tins, Model master and floquils are bottle, and rattlecans are, well, cans lol.
i dont have any alternate versions specifically because i always paint in enamels, so thats all i use. I stick with what i know works for me, which took quite a while to nail down the colors/techniques.
As for availability of acrylic versions of these colors, Humbrol makes acrylic versions of most of their colors. Model masters does as well, but i dont know how many they actually DO make in the acrylic versions. I always used enamels so thats why the list is what it is. Floquils are also getting harder and harder to find, because they have been discontinued since 2013, so those colors could be an issue. I usually find them on e-bay.
Megahobby.com is where i usually get all of my paints. they carry Humbrols, Testors, testors model Masters, and tamiya. They are in the US though. Humbrols should be easy to find where you are. and colors like the rust can be humbrol, i just happened to have testors rust on hand so that why i used it.
There is a new brand on the market in the UK, Archive-X, they make paints specifically for what we are doing to match ILM used floquils. (They are a member here by the same name) I will eventually be switching over to those but i dont know what colors match at this time, as so far ive only seen an ESB helmet done in their paints. They currently have enamels and last i spoke to them, they were currently in testing for the acrylic versions. I may switch to acrylics once they release theirs if i like them.