Paint Playmobil or Lego (only armour) is very easy.
Personally I prefer to use Citadel colour (Yes, I'm a Warhammer fan)
DO NOT DO THIS INSIDE. GO OUTSIDE.
Unless you have a breathing mask...
First thing to do is pick up all your amours helmets etc etc and place them on a cardboard box.
Now get ready to spray it with some black (Chaos Black from Citadel)
Try to spray the colour from every direction, do not worry if you think is too much, It will dry.
To get the metal look spray everything with this:
Lead Belcher (the new Boltgun Metal, if you are old like me)
And this is what you get. Let's put them on!
Good to go. Still missing is some black ink to highlight the armour parts and make the metal look real and worn.
This is the final result. Now we have to paint armours for an entire army, yaaaayyy