MiGMan's own Cougar throttle. Notice the area of wear.
In the centre of that area I first applied a couple of strokes of clear nail varnish.
I could have used black varnish, but the intention was to see whether the edges of the exposed paint were protected - they were!
As expected, the nail varnish has prevented any further moisture damage to the painted surface. The main concern I did have was of an adverse reaction with the paint. There was none after 3 weeks of hard use .
Now I can proceed to coat the area of most wear - where the palm of the hand rests on the throttle.
Paint degradation on a flesh to painted metal interface will inevitably occur - it's just a question of when - see Paint - conditions of use.
The only ways I know of to prevent this in manufacture are by using baked enamel coatings, which is a more expensive process. Note that it apparently even military controllers are only spray painted. (Also note that I am not an expert in industrial finishing.)
If you are really worried about this effect I advise: