I had to compromise, keeping an accurate inventory was too much work. Now using plastic bins organized by area or function with parts in appropriate containers, from plastic bags, smaller boxes to new packages. Other C&V and/or bike flipper guys I ride with do this and it works for me as well. Examples:
Saddles bin- loose saddles, bagged posts, bag of loose post/saddle parts, bag of clamps and clamp bolts, etc.
Shifter bin- shifters in bags, bagged repair parts (hoods, levers, etc.), new packages of parts like Campy G spring 4 pack, etc.
Cassette bin- loose clean cassettes, bagged dirty cassettes that I think I will never use but may use a sprocket or two, bags of cogs, loose spacers, etc.
I maintain bikes for three daughters, two sons-inlaws, and a granddaughter, as well as my wife and my fleet, almost all C&V.