Thanks- Here is some tips on the helmet:
Base coat with your favorite Tamiya Color-applied with airbrush. I shaded it with a slightly lighter color on the top and edges. When dry, coat with future or similar gloss/semi gloss acrylic clear. When dry, give it some washes with brunt umber, raw umber and sepia oil colors. Let sit for 20 minutes or so. Use a slightly damp brush, remove excess oil colors. You'll see when to stop. When dry, dust helmet with dirt color pigment. Use some enamel thinner to apply localized washes around details. Feel free to remove pigments to your taste- light dirt, heavy dirt, etc. Usually rub it with my finger. Grind up some pencil lead on a sanding stick or sandpaper. Use the finger to pick up the graphite dust and rub all over the helmet. You can use your clean finger to remove excess or slightly wet your finger to do that. If the helmet is too shiny, I may dust it with a spray of Dullcote from the airbrush. Last step is to rub a pencil lead on the edge of the helmet- or you can use a silver artist pencil to do this. The silver will be brighter.
I hope this helps-
Matt