Best set of tutorials I've seen out there. The Painting Buddha guys provide this for free on youtube where DVD of tutorials of only part of what these guys provide and not as nicely produced are $30-50 USD.
Share and Enjoy these with anyone wanting to improve their painting game.
Ultramarine Painting Tutorial Playlist - Armor, glazing, weathering, helmet, Object Source Lighting, True Metallic Metals, blending...they do a great job of teaching all of these things and more videos are being released.
Please consider checking out their patreon site as well to keep them producing this type of tutorial!