Once they are clear just use a polish made for plastic to maintain them . The only reason they cloud is they are overlooked and need to be a part of regular maintenance . I don't think clear paint would stick very well to a polished surface like the lamp lens .
Nearly all plastic light lens do in fact have a coating on the exterior that is REMOVED during the polishing procedure to clean them up and they will cloud over even quicker each subsequent time. Applying one of the headlight films will prevent the surface clouding from UV degradation of the plastic lens.