Gettin' there, Owl... Love the way you made the detail pop on the undersides, and the wheel-bay detail too.. Yer gittin' to be quite a Gizmologist indeed.. Steel wool is one of my favorite tools, too... I use it a lot with dents in aircraft skins (make a dent by slicing a chunk outta the styrene, then rub steel wool on it until it feathers-out. Really works well after "bouncing" a 1/4" Round steel-cutter bit in a motor-tool around the various areas that would likely get dented)... Also works well for depicting the aluminum patches that were pop-riveted on to cover any skin damage from bullet and AAA shrapnel...
(I think folks forget to show previous repairs on aircraft that are being modeled as having had dozens of mission in harsh climates, with maintnence performed under primitive shelter & working conditions.. Even a blind pig will find a truffle now and then, and the AVG pilots were no exception to picking up a stray hit now and then, lol..)
Not sure about dot-filters though... That technique's a little heavy-handed for aircraft (as are a few of the wash/dry-brush techniques) as, while armor gets filthy, airplanes merely get dirty.. It's strictly your call, though... I ain't sayin' , "Don't do it", just saying that I probably wouldn't... I like the control I get with pastels.. Dot-filters, like diamonds, are forever...
Although, upon reflection, there are certainly areas of the aircraft that could benefit from it, areas like aft of the main and tail-wheel wells, cowl-flaps, tires, and exhaust... I'll wait and see how yours looks before I try it, lol.. Anyone else use dot-filters on A/C? Lemme see it..
Just a "head'sup", BTW.. Powder-stains from blast-residue would be seen on the fuselage aft of the fifties, but the .30-cals wouldn't do it.. 'Cept the shell/link ejection-ports, that is (don't remember if the model has those molded or not though)...
Gun muzzles that protrude from the wings more than an inch or three don't stain the wings, nor muzzles that are inside blast tubes, ala P-47/F6F... You and the rest probably knew that already, it's just a reminder...