I don't think there are any good answers to these needs - they all
depend upon what the specific conditions of the gelcoat, vinyl &
plastic lights are. in general, intact gelcoat is easily cleaned with
almost anything nonabrasive whereas faded or weathered gelcoat is
porous and a whole different problem. Anything containing any kind of
silicone is long-term death to vinyl and plastics as well as rubber,
except for pure silicone grease which is not a cleaning matter. There
are several different plastics used for windows (lights) which differ
slightly as to how they like to be treated and any kind of wax is crap
on clear plastic; some plastics cloud and some don't, under some
conditions & not others; plastic polishes like Novus or MagGuire's
restores 'em all like new after the easy stuff has been washed off, but
takes some physical work & time to do right. It someone sprayed Pledge
on my plastic ports I'd be tempted to shoot them. People bleach porous
gelcoat every day, and Scrubbing Bubbles may work great on it & is
worth a try, but the best porous gelcoat cleaner commonly sold is the
nonskid deck cleaner (even though it's not a nonskid deck) that
penetrates when scrubbed in & is rinsed away. It also cleans stained
shoreside showers/tubs that are dirt-stained beyond Scrubbing Bubbles
or Tilex & I used it for that in a rental property. Waxing porous
gelcoat is also futile in terms of time/results/protection, machine
polishing it is a total waste of time because it just opens up more
pores, the Penetrol trick is less than claimed as a solution, & its
better to paint it for real to professional standards so it is easier
to clean & maintain. Imron is harder than gelcoat & impervious to
grease.