Hi Paul
I've used different methods in the past but in this case i just mixed lamp black and burnt umber oils and applied it to the bare metal without any thinners added.I put it on pretty thick,so i dab most of it off with a soft kitchen towel leaving a thin skin of oil paint.I then take a flat chisel shaped brush and just dab it until i get the desired effect.I used the same method with the scale armour but i used a larger flat brush and gently brushed upwards to remove some more oil paint from the tips of the scales.When this is all dried ,usually about 2 to 3 days,i use straight lamp black with a touch of thinners to ouline certain areas i.e.between the plates on the arms and the helmet etc.I used silver printers ink mixed with the basic oils for the rivets etc.
Brian