Ok, so you want a realistic, earth duty, Mass Production model that looks really good, right? Well, one simple, and nice looking technique is camoflauge, either airbrushed or drybrushed. This technique can be adapted from any Armor technique onto Gunpra fairly easily, and is incredibly eye catching. First, you need to determine how deep you want the colours to look. The depth of the camo can be hazy or very dark. If you want it fairly consistent, then the airbrush is your choice, but if you want some variation in colour depth, then the aerobrush is the way to go. For either of the two choices, you have to mix your colours first, and keep them in small paint tins or jars. The preferred paints are enamels, because they provide a better militaristique look, and tend to have more reflectance texture compared to acrylics. You should basically mix 3 different shades in three different bottles with maybe 1/4 thinner. The most basic is a dark gray, tan, and some type of green. Now, you're set to airbrush or drybrush, but first, you have to prepare the surface. You should have the surface well sanded and smooth, and (optional) primed with black, silver, or gray, depending on the final look you want to achieve, black being darkest, and silver being brightest. At this point you take your pencil, and etch in where the basic outline of the camo spots should be. Make them consistent, and try and be creative with the organic-ness of the spots. Once you're done spray with some overcoat if you prefer, and then you're ready to camoflauge your model. Set your airbrush on the lowest possible psi if you're airbrushing and test spray on some styrene to get the preferred flow you want. Switch colours every other spot of camo and DO NOT MASQUE! That is the most important part. If you do masque, the colours will not blend well and won't appear realistically. When finished, overcoat with flat finish. Drybrushing appears a whole lot more realistic. Prepare your nylon head brush by taking your bottle of custom mix paint and put the top on. Shake the bottle. Now pick up a consistent amount of paint from the inside of the cap with the brush and tap on a piece of cardboard until the paint is somewhat blotchy. Now, tap the tip of the brush on the model until the appearance is to your liking. Repeat this until the whole surface is covered with the colours of your choice. If you drybrush, you always have the risque of the camo looking bumpy, due to the paint not being thinned well enough. In that case just sand it off and thin your paint out so you can try again.