I usually start with a base coat, then add small blotches of color with the finest brush I have. I don't like using washes on my infantry as I think they make them not pop as much, but my inexperience might be the cause of that. Painting packs, launchers, boots, face, etc... is almost always worth the extra effort.
My first attempt at multicam, I think I need to be more patient and try to make the camo blotches smaller for the black and off white colors.
Some extra details I like throwing in are balaclava and different colored weapons.
I always test out ideas I have on 1 or 2 minis before I paint in mass quantities.