Base 'unit' before specialisation

1. Prime Chaos Black or equivalent.
2. Heavy drybrush/overbrush with Thrash Metal
3. Cover entirety of model with Vallejo Environment Effects Rust Texture. You can use Typhus Corrosion , I just prefer Vallejo's for large steps like this (TC works better as a finishing 'stain' or grime effect than a rust-texture applier).
4. Drybrush model with Thrash Metal , then a light drybrush of Speed Metal
5. You can pick out the more tube-like metal parts with some Basilicanum Grey to add variance to the inner-workings, but this is highly optional.

Fireman

1. A note on the base - this model has a metal-sheeting base if you're using the resin one included. I simply applied the above steps also to this base. When finishing the model, I picked out the wood beams with Zandri Dust , the other detritus with Old Copper , then washed the whole thing with Basilicanum Grey before painting the base rim.
2. Stipple Mephiston Red over the relevant panels of the model. There are two ways to do this - super thin and lots of thin coats to build up texture, or relatively thick and rough/scratchy to apply a more scraped effect. I went with the latter, but use the prior on Ork vehicles and enjoy the effect a lot.
3. Stipple Averland Sunset over the central head unit, emulating the star seen in-game. You could also add a blue dot in the centre, for which I'd recommend Cantabric Blue , but I didn't bother. I'll likely build this up with a few more layers at a later date, but was trying to speed paint these protectrons.

Police Officer

1. Stipple Mediterranean Blue on the relevant panels - same idea as the fireman, where you can either go thin or thick. For the police unit I went thin, so the blue appears a lot more metallic IRL.
2. The siren/hat was overbrushed with some Mephiston Red . I was trying to paint these guys sub-1hr, otherwise I would have probably made this look more like a plastic light than a metal cap.
3. The 'face' panel was stippled with some Pallid Wych Flesh . White felt too clean, but PWF has a level of grime to it when in situ to the metal.
4. For the holotapes on the ground I picked out the edges with Tau Light Ochre and the metal with Thrash Metal