I use liquid hand soap for a lot of these tasks. Essentially no possibility of degrading the material and in the case of anything rubber on the aspiration side of the engine, no silicones that can degrade (jacket) the oxygen sensors or catalysts.
No, OEM projectors with HID were a good option before LED became viable but unless you're using a projector housing the whole HID capsule emits light so a reflector assembly built for a point source (filament) will just turn into a glare factory with a HID retrofit. Your own distance vision will be degraded by rayleigh scattering and any dust or vapor in the air, and oncoming drivers will find you a most unsociable individual.
It's disappointing that nobody is making ~4000k-4500k headlight LEDs which more closely match actual surface daylight temps, seems everything is either 6000k which disappears on wet/dark surfaces (deer in the rain, log/rock in the road..) or selective yellow which is annoying and also doesn't give you much detail back from things which don't have a high contrast to each other (coyote in the desert for example) . I can buy 4500k LEDs for my household lighting... just not for headlights. Bleh.