Like while Painting Chrome, this was another attempt that showed me I tend to "paint from the hip" so to speak. My untrained eyes do the best I can, but I prefer to paint what I see, not necessarily what there is to be seen... if that makes sense. So I'll offer some tips to give you the general idea.
A Matter of Perspective
So the tricky part of painting metals with realistic reflections and shines is that it's VERY dependent on a lot of things. Where the light source is and the placement of the object will drastically change the appearance. The trick is that you'll also want to make all the metallic parts on him seem to be lit from the same angle. Take a look at the below photos.
If you're doing a bunch of full models like this, then one option would be to get an extra one and paint it silver / chrome. This'll let you set it up somewhere to use as reference.
Painting the Effect
When painting these, I decided to start with boltgun. (dark silver) This sets the tone for the whole miniature. There's really no wrong decision, as long as you try to create the same effect over the whole thing.
The next step was to paint dark grey between the boltgun and black areas. (More on the underside.)
Next up (visible in the 3 photos on the left below) I simply washed with black.
To finish, I used silver paint to highlight TMM areas.
By Mixing Metallics, I'm also showing how TMM can add a contrasting shine to NMM armour and weapons. Below you can see how even at different angles, both the TMM and NMM still look different.