Drab green and brown: Flat, Semigloss or High Gloss?

For me, it varies. If it's small detail work, I generally use a brush with flat Testors or Tamiya bottle paints, which come in a great variety of colors.

If it's larger, I will use Krylon paint, generally in a flat or matte finish, unless I'm looking for a particular color and it only comes in a semi-gloss or gloss paint, in which case I will use a clear matte finish or Dullcoat to take the gloss off.  

I also use black and rust colored washes and a variety of soft chalks for weathering to get the result I'm looking for. 

The real world tends to be flat, not gloss or semi-gloss.    This is due to textures, and dust and everyday life.    Also in most cases the colors do tend to be muted rather than really bright.

Most modelers these days use ground foam from Woodland Scenics, or Scenic Express or some other outift to make ground cover.    There are lots of colors and textures available.     I paint the wood surface first but the color is not too important as long as it an earth tone or green shade.    After this is dry, I wet the area from a spray bottle with "wet water".    This is water with a few drops of detergent added.    This breaks down surface tension.    Then I spread a mix of about 50% water, 50% white glue on the area - this is very liquid so you need to protect things underneath.    Then I sprinkle on the ground foam.   I like to vary the colors, so I don't put down all one uniform color.    I generally put down a lot of browns and greens in a splotchy mix.   Closer to the track I use more browns since the trains and clearing would kill the grass.      For O scale I use mostly coarse, and some medium textures.    You can alos get foilage clumps.     I don't mix the stuff and put it down,  I sprinkle it on then add some other colors next to it or over or whatnot.     The colors are still probably too bright, but much better than paint alone.      You need to let it dry generally over night before doing anything else.

The rattle-can "Camo" colors are wonderful for all kinds of scenic uses. They are ultra-flat. 

My layout board is already painted with white Kilz II latex  primer, to seal it.   It will hold any type of acrylic or latex paint very well, but I'm not sure at all that any type of white glue mixture will stick to it.  I guess I will go with the ultra flat Krylon paints, and then put patches of the glue mix and ground cover on it in test spots.

I am a little concerned that if I spray down patches of drab brown paint and drab green paint, I will have a layout board that looks like the old WWII camo pattern worn in the Pacific.  I guess I should do it in a random pattern, but pay attention to where buildings, roads and tracks will sit, so that it looks more realistic.  

Thanks for all advice.

Mannyrock