Like a "designated spokesman of Cz What if SIG" I was charged for translating answers on Your questions...
The Big Gimper asked for weathering...
For "normal" colours comrade Ujik used preshading....and for metalic colours for change postshading (with slightly darker hue of original metall colour)....
I hope,that this answer is understandible....
I´m sorry,but You must excuse our, "poor eastmans",because in School we (mainly we "early-borned") we learn only russian...and english is for us slightly difficult,then russian....