I've lacquered a few parts for a bike using two different lacquers, and got very different results.
First up was a stem, given several coats of Plasticote lacquer.
It looked great for a couple of days then the whole surface crazed.
A couple of weeks later and the laquer has so many tiny cracks in it that the surface looks white in places.
I don't think it's due to heat/cold expansion/shrinkage, I'm thinking maybe the surface area of the stem was too small and with time the lacquer has dried out and contracted too much.
I'd polished the stem with Autosol beforehand - maybe there was some chemical reaction with the lacquer causing the cracks?
Secondly I gave a set of forks several coats of Simonez Acrylic lacquer - no problems here, it's still perfect after a few weeks.
Lesson learned, I'll have to strip the stem and start again.
This lacquer makes the bare metal underneath look darker, not sure if it would have any shade effect over paintwork.
I saw Cellulose lacquer and petrol-resistant lacquer too in the shop, it was confusing guessing which type to get.