Drybrushing is a very old technique, and means using a regular bristle-type brush to highlight small raised areas of the kit you're building. Try the following:
Get a nice, small brush that is clean, with a minimum of stray bristles, preferably none.
Dip about 1/3 of the bristles into the paint, then remove it. Immediately start wiping the brush on a papertowel or a cloth to remove as much paint as you can. Ideally, you should be able to still see paint on the brush, but none will rub off on the cloth.
Use what is left on the brush to LIGHTLY brush across raised details on the kit that you're building. I usually use this technique on a radial engine cylinder's cooling fins, instrument panels, etc. Anything with raised details that I want to highlight. It works very well, after just a little practice. Hope this helps you out.
As far as B-52's go, sorry I can't help you there. A 1/72nd B-52 is gonna be one huge kit!! Good Luck!!