Weighing anything at all without calibrating the scale is pointless. Scales that are not possible to calibrate are useless from the factory 
And calculating the weight of paint is very hard when dealing with such a small surface area and thin coats, it all depends on the composition, while a wrap can easily be calculated if you have the exact surface area, the base vinyl material specs and know the printing method. Most companies selling wraps could probably give you the exact data for that.
I bet that the thinnest possible decorative coating would be hydro dipping. The applied film is super thin.
And calculating the weight of paint is very hard when dealing with such a small surface area and thin coats, it all depends on the composition, while a wrap can easily be calculated if you have the exact surface area, the base vinyl material specs and know the printing method. Most companies selling wraps could probably give you the exact data for that. I bet that the thinnest possible decorative coating would be hydro dipping. The applied film is super thin.
