For the past few years I have been using toothpaste to clean and polish Katie's portlights. It works pretty good, and is usually around for use. Prior to that, I used a rubbing compound/wax product for fiberglass, but it didn't last very long.
Then this spring I had an idea, after seeing a TV commercial; I went to the store and got one of those automotive headlight polishing kits.
Have to say that the results do exceed those of using toothpaste. The kit I have comes with 4 grades of foam-backed, very small grit, wet-type sandpaper, a bottle of 'lubricant', another of 'clarifying compound', and a moist towelette-type wipe that is labeled "Lens Sealant". I did not use that last piece of kit, and the ports still look good. I think the whole thing cost $10-15, and it seems as if it will last through several more polish cycles.
From my experience any wet/dry paper above 1000 grit should polish plastics--1000 may not make it really glossy, 1500 grit should be acceptable--depending on material---2,000 grit will make it glossy-- the auto paint store I deal with stocks paper to 2,000 grit. Up to 12,000 grit is available. Of course the finer the grit the longer it takes--I use soapy water for lubricant--no special reason.
Stuff like this seems to work....
http://www.griotsgarage.com/product/car+care/glass+cleaning/fine+glass+polish%2C+16+ounces.do
http://www.griotsgarage.com/product/car+care/car+polishing/car+polishes/plastic+polish%2C+8+ounces.do
any product that is abrasive can be used for polishing. Tooth paste is a good illustration. Since the aggressiveness (size) of the abrasive is related to the time it takes to get the desired result, i prefer to use wet/dry paper. That allows me to try different size abrasives to determine which one i feel is best for the job, and the result i want. I also think it is cheaper to stock different grades of abrasive paper than prepared products. Toothpaste and baking soda are cheaper,however they may require a lot of time to get the desired result----having said that any abrasive will work---sand would be great if there was a way to sieve it to 1,500 to 2,000 grit---wish i knew how to do that!!!!!
On the C-26 companion way I was able to take them from
(http://thumb1.webshots.net/t/96/196/5/5/4/2285505040101866121XeHoKm_th.jpg) (http://good-times.webshots.com/photo/2285505040101866121XeHoKm)
to
(http://thumb1.webshots.net/t/77/77/6/76/28/2046676280101866121mnrgGg_th.jpg) (http://good-times.webshots.com/photo/2046676280101866121mnrgGg)
with wetsanding with 1000 grit then 2000 grit sand paper then 3M's fine rubbing compond
WOW....guess there is hope for old plexi