I haven't done any ashigaru as yet, but this is what I did for the black armour on those of my samurai who have it:
1. Undercoat entire figure in matt black.
2. Dry-brush entire figure with medium grey.
3. Paint and ink-wash everything as per normal, including any lacing, EXCEPT leave any armour itself in its black/drybrushed grey undercoat.
4. Varnish the entire figure with your normal matt varnish.
5. Ink-wash ONLY the black armour parts of the figure with GW 'devlan mud' wash (the wash dries to a slight sheen, which makes the armour look slightly shinier than the clothing around it, but not as glaringly shiny as gloss varnish).
The guy second from left is done as above. And the guys on each end, whilst their armour isn't black, have used the same final ink-wash step to achieve that egg-shell sheen on their armour and helmets.
