The good news is that when it comes to professional restoration there are only two main methods The classic buff and shine done mostly by auto detailers, and the Modern Permeant Restoration For years auto detailers buffing the lens, and home remedies were the only option to clean the oxidized lens. These methods can make a difference by removing some of the oxidation that forms on the lens, but they have few major flaws and damaging side effects.
In more severe cases where oxidation has started on the plastic itself, buffing alone cannot fully remove the oxidation so surface cleaning remains the only option, but most importantly they have no means of replacing the protective coating they just removed. Auto detailers may use wax as an alternative. Wax is meant for clear coat on the paint and is not a durable option. A simple carwash is all you need to wash of the wax leaving your lens exposed to elements significantly shortening its life. Without protection instead of the coating getting oxidized the plastic itself starts to break down. If not treated the damages lens may start to have spider web cracks and fractures.