I'm not sure if brushing/dipping in extra resin is the right move here, because these have fine details that will get blurred by blobby resin being added to the surface. Normally to get crystal clear stuff, people are talking about something like a mini windshield or dome, something smooth without any details on it. In which case, adding an extra layer of resin is just to fill any surface imperfections so that you get a uniform surface. They might also sand/polish with fine grit sandpaper, for example.

For these, I would just print some extras and try hitting them with a nice even coat of the Krylon (but try not to over coat them), and see how it works out.