I don't entirely agree with Doogs tutorial. First of all there is only one type of black and it's simply toneless, no variation what's so ever. Anything else is simply variations of very dark gray. Pure black does not exist in nature, it is a man made "color", just like true white. For the sake of discussion, we will call them colors. Considering that good practice when painting, it is always recommended to start with the lighter colors first, when trying to achieve a black weathered finish, one should start with a dark gray base and work towards the black in progressive transparent coats of darker gray. Accenting the panel line can then be done using a black wash or lighter gray for contrast. Never do a black base for as a start, otherwise you will make things harder on yourself. The T-38 example is more of an automotive type finish and simple gloss black should do the trick. An F-117A or P-61 should be painted with progressive transparent coats of darker or even black in some areal to obtain the right effect. Remember that a flat black/black gray finish is very prone to weathering showing off its base pigmentation of dark blue/brown/green tones. Look at how painters work to achieve dark tones in their paintings. Personally, I never use use pure black anywhere unless it's a wash, and only under certain circumstances. Just my 2¢ worth here.