Why do you have so many dirt textures?

You can share it on Slack

Can I have your model file, please?

Also mapped dirt uv for every dirt texture

I set 2 UV's in every material, set dirt texture in each one, still can't make it to work.

Each texture must have UV map set where UV settings are

It has actually 2 materials, so it uses 3 textures. 2 main textures and one dirt texture.

You can use powercell as an example. It has two UV maps. Main texture uses the first one, dirt texture uses the second one.

I think yes

Do you have UV maps used in each material?

Another error http://image.prntscr.com/image/63b5cd071...85eba4.png

You need to go to mesh's properties and add a second UV Map, this one is for dirt

You need second UV Map for this to work

http://prntscr.com/cydh1c What's wrong?

Good to know, thanks

I added name aliases because it's easier to remember. You can add many states, separated by commas. Like, [normal,part3]

Or was it 1024?

1024 is an explicit state number. part3 will be translated to 1024 automatically. Whichever you prefer.

Do I need to translate state numbers to strings, or it doesn't matter if it's [1024] or [part3]?

All that matters is that you set correct state, texture name and material properties (diffuse 1.0, ambient 0.5 I think). Vertex group will be found automatically. UVs you set don't actually matter, if I recall correctly. They are recalculated anyway.