When I was in college I was on a underwater robotics team. We were having an issue with the water rising our brushless motors. We figured we would need some sort of enamel coating that could be applied in a this enough layer so that it wouldn't slow down the motor casing.

We looked up how much something so specialized would cost and it was way out of our budget [very small because we were a community college]. Then I remembered some random fun fact that I have no idea where I learned it from: nail polish has enamel varieties and it even came with a tiny applicator [brush]. Cost is about $5 in 2013 money.

We took 5th on that years MATE competition and built the bot for $1500 [we got the "Biggest bang for your buck" award.