You've outlined a good method for cleaning out the inside of the Hella 450s headlight housing. The key is to use a high percentage alcohol, such as isopropyl alcohol (IPA), to break down and remove any residue or water spots, then use a low-lint cloth or Q-tip to wipe the inside of the housing. You can also use a microfiber cloth to remove any dust inside the housing. Remember to
take safety precautions such as disconnecting the battery before cleaning the headlight.