the quickest way to paint these things is with spray, or aerographer. you just lay them in a surface and paint them all at the same time (those with the same color, of course). if you don't have spray, arm yourself with patience and paint them by hand. it's not the same, but it's a good de-stresser lol.
instead of masking and then painting, you just glue them already painted, and where the glue rubs off then you just correct that part (if you really need to, if it's small and off view, don't bother)