Cleaning reflectors with 99% isopropyl alcohol?

Can I clean reflective part of the reflector with isopropanol and be sure it won't damage the surface?

yes you can.

I bought a hood from a guy that smelled like a moldy wet towel left in a pile of leaves once. Disassembled and sprayed with isopropyl in an automotive paint gun. Worked better than anything. Even sprayed inside the ballast. The alternative was fumigation with formaldehyde as I've seen that done with vintage audio equipment left in a mildewy attic.