Weathering ?....................what is it in actuality ?
=The effect of the weather, service life, environment, soil exposure and its mineral effects on metal or paint, ultraviolet exposure, dust, metallurgical content in the vehicles construction...............etc etc etc
HOW ? can anyone predict or otherwise stipulate any form of consistent "weathering" methodology ??
If they can, I want to read it.
Even Mr Jiminez only uses his minds eye interpretation and skilled execution of what his model looks like the day he does it.
Its a model- a representation of what the builders educated guess is of what it might have looked like if it were a real machine.
Sure, we know water runs down a vertical surface, and would pool on a flat one blah blah blah, but as for 'right' or wrong
?? 
Mark my words Sir, it will all come together when you get the upper onto the lower and tie them all in.
Any man that produces an AFV with an open fighting compartment deserves a medal.
what I do when applying streaking effects ( i normally use ak interactive products) is i use another brush with just thinners on it and feather out the streaking until you reach your desired result, if you take too much off with the thinners you can always go over it again with more streaking and so on, this is the method that has worked for me over the years, HTH 
