Ben,

A "polish" is one of those words that gets to mean many things in automotive detailing. I would define a polish as anything you apply to the surface that is NOT a wax, and does not remove paint. (swirl removers, "cut" type polishes) What a pure polish does, a favorite being Meguiar's #7, is remove surface contaminants/oxidation/dead wax when applied/removed to the paint. Think of it as deep cleaning... All of the products listed in this post work on all paint colors as far as I know. The exception being the 3M swirl mark removers that are coded/labeled for "light" or "dark" colored cars.

As for water spots, they can do some damage to the paint if left unattened, especially on an unwaxed surface. The cleaner the surface of your car is and the better wax it has on it when you do get hit with a water-spot situation (as described in the thread above) the better your chances of coming out of it without any headaches beyond a polish/re-wax of the affected area. Let the wax take the abuse...

If the spots are on/in the paint, especially old or really deep you can either remove paint via the cut-type "polishes" or shine it up and ignore it. If it is something on the paint (as opposed to "in" the paint) then clay or cleaning type polishes are the route to take. (pre-wax cleaner, clear coat scrub, #7, etc) Clays are their own breed, run a search to get the info there... BTW, I would always start with the cleaning type polishes/approach before using the cut-polish method.

If you have already done the above and have some really nasty spots then I recommend taking whatever your trusted cut-tpye polish and applying it only to the spot itself on the tip of your clean fingertip. As for "trusted" I recommend meguiar's fine-cut or especially #9, or the 3M equivalents. The 3M's tend to take a bit more elbow grease to work, but either lineup is an excellent choice. Again let me state that multiple applications of a less agressive product is superior to one application of something harsher. As always, once you do use something harsher, follow it with the next less agressive on up the lineup through cleaner type polish and eventual waxing.

For waterspots on trim, that can vary quite a bit. If the trim has a "nap" or texture to it, a toothbrush (soft bristles please) may help along with the standard 100% cotton terry. Look for something that cleans trim vs "conditions" or "dresses" it. You can even use a bit of household cleaner on the plastic trim parts for really stubborn stuff. Back to Black is popular along with the Meguiar's equivalent. Once you have removed the spot, recondition/dress the trim. I like Meguiar's Endurance personally. Put on a rubber glove, massage endurance on/in with your fingertip for at least 30 seconds. Let stand a few mins, wipe with terry...

Give the above a try and let me know how it works...

Hope this helps,
Lee