Motors are brushless, nothing to short and no issues (except maybe bearings). Electronics could be coated but not sure what you would effect like the barometer which needs to breath to work properly. I'm not familiar with the rustoleum product as a 2 part system. You don't need to cover the vents if the electronics are protected; you don't want water to collect and puddle inside. I won't say it wouldn't work, but it could be costly if you get it wrong.
The camera, optics and complexity of the gimbal are a whole other beast if you are planning on flying those in the rain.
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