Dry Brushing is the easiest technique, you can do a little then build it up. I use Tamiya Colours:-
Xf1 Flat Black
Xf2 Flat White (a surprising one but helps bring out detail)
Xf9 Hull Red (great for rusty effects)
Xf24 Dark Grey
Xf49 Khaki
Xf52 Flat Earth
X29a Thinner
May appear a formidable list but all have their uses.
Not sure if you have tried Dry Brushing before so I will describe how I do it.
I use a pretty largish hard bristle brush (around 10mm). Mix the paint up very well with a Screwdriver the wipe that with a cloth, run the brush iver the residue on the cloth then just a quick flick to get hardy any colour on. Best to test on a piece of scrap till you understand the effect that you wish to achieve. If it is not enough you can always do more, too much and a wipe with some of the Thinner. You can also use some of the thinner that you have been using to clean btprushes to give a sublte wash in places.
Of course any Matt Colours of different brands but similar colours will have the same effect. I just happen to prefer my Tamiya.