First, of course, you can brush paint them. Use a 10/0 filbert tip brush or 20/0 spotter tip. Use Vallejo paint, which brushes like magic and won't look like blobs of paint on your camo.
Second, you can airbrush them freehand. I have a Tamiya HG
that will shoot the dots fine enough. You have to turn the pressure way down, thin the paint 50/50 or more, and get real (like 10mm) close to the model. Practice A LOT on a plastic card first so you can do it without spattering.
Third, I've developed my own stencil method. Get a sheet of thin (.005) plastic, about 60cm square. Drill small holes in it in small random groups for the "dot pattern". or, cut tiny triangles in it for the "taco chip" pattern. Alternatively, you can also use a circle template to cut rings in it for the "octopus" pattern. Place the stencil on the model, shoot a small area at a time, and lift the stencil straight off. Instant airbrushed dots that blend right into the camo. This method works the best and is nearly foolproof, so I reccomend it.
Try all 3 and see what works best for you. I hope this gives you some good ideas, have fun.