The only "aging" I've done to my builds is applying 44/40 cold blue to the brass and rubbing most of it off.....yields a less shiny brass w/ some darker areas in the corners, etc. My intention isn't to age the brass, but to reduce the shine, accentuate the shapes on say a TG and high light the engraving.
Aging the brass , putting pitted surfaces on the steel parts and doing no aging at all to the stock seems to be an incomplete job which doesn't fool anyone.
Aging a rifle to simulate or copy an old original is different because a complete aging will be done....including the stock. ......Fred