Dear Spencer,
Many thanks for your query.
This is how I paint chainmail:

1- Black undercoat - usually GW Chaos Black spray
2- I then mix a very dark combination of GW Bolt gun metal and Chaos
Black which goes liberally over the required area, don't worry too
much about getting it in between the raised chain links.
I use a relatively flat brush for this next stage which is a little
like dry brushing, but what I do is use Bolt gun metal straight from
the pot, nice and thick. Load up the brush and wipe off as per usual
for dry brushing but then drag one way, usually against a grain if you
can find one. For chainmail this is usually top - bottom (ie where the
light is coming from) but never across the figure as this tends to
give too much coverage of the highlights.
3- Repeat on the extreme highlights with Foundy Spearpoint.
For chainmail I find intermediate shades tend to blend too much
without effect.
For plate armour I would recommend intermediate shades.

I like Bolt gun metal as it is usually quite thick and gives good
coverage. I use the same method for Musket barrels, as I like the
contrast between the dark basecoat and the extreme highlights.

By the way, was looking at the Front Rank French Naps on your site the
other day, absolutely superb. I will soon be delving back into that
period for my own collection. Watch this space!

Kind regards

Martin