Since I'm going for a very lightly weathered look, my weathering tools on this project are very simple.
A rasp, 0000 steel wool, non scratching 3M pads (the blue ones), Brichwood Casey Aluminum Black and Birchwood Casey Alumium Black.
For the weathering of the brass parts, I use a small paint brush and brush on the brass blackener in very light and even coats and then scoute the brass with the steel wool.
For the weathering on beer tab, I brushed on light coats of aluminum black and hit it with the steel wool.
To weather the slide switch and the clamp lever, I hit them with the 3M pad, followed by aluminum black and steel wool.
For the Kobold clip, I scoured the clip with the 3M pad, kit the corners and various areas with the rasp, hit it with aluminum black, then scoured it with the steel wool.