My advice is not to use brushes or pencil's.Use dodge and burn tools!
Ok lets start by selecting body armor making new layer and filling it with grey color:
Now go to filte/sponge (brush size 0,definition 0,smoothness 1)
Next is to select dodge tool (small size,range:highlights,exposure:10-15).
After you add some highlights add some shadows with burn tools (same options!):
Its look pretty good but its not finished!We need boobs!
Make new layer nad use Eliptical marque tool and make circle for boobs.Fill it with a bit darker grey than armor.
Go to blending options and use this:
Now select body armor again go to blending options and use this:
After we did all this flatten the image because we do not need all this layers no more:
To make this METALIC armor more realistic use small brush pick light grey color and start painting some scraches:
We are almost finished.Now is all to you if you want do some more shadows or highlights or add some nice looking detail to armor:
To make this detail i have no explanation.Use small brush and paint it and after that use in blending options same options like here to make it engraved:
I hope this was useful so comment and thanks for watching!
Oh and I forgot.When you use sponge tool go to edit and fade and click on 45.