Well, thanks to Cathy's rather short PM

this thread got my attention.
First off,
you need to identify what kind of watermark etching does your car has. This is broadly classified as "in" the paint or "outside" the paint. "In" means that the watermark etched into the paint layer, "outside" means that the watermark due to mineral deposits on the paint surface.
1. If you throw X acid to your paint and let it sit around, what you have is a "in" paint etching.
2. If you have water on your paint and have it bask in the afternoon sun, you probably just have the more common "outside" watermark deposits.
3. If you have a car and expose it into the elements (rain, sun, bird droppings, rinse & repeat) for a long time then you probably have both "in" and "out".
Anything that manages to eat into your paint layer means that it's potent enough to penetrate your other layers.
Since
I believe you have #2, I'll go more in-depth on that one here..
So like.. what are these "deposits"?
These deposits are hardened water mineral deposits. Think of them as a cave's calcium carbonate stalagmites/stalactites but on a microns scale and stuck to your paint.
How do you soften them?
If there's not much deposits, just washing your car will do. If the deposits are more hard-headed than your average <insert annoying boss here> that then it's time to use chemicals to help you out..
Let's say you need the chemicals, what's the cheapest thing to throw at them?
Probably either diluted vinegar or isopropyl alcohol.
I'm too cheap for those two, what about something "free"?
I believe your urine is acidic AND free. I still won't recommend peeing on your car though.
How do you apply these?
Uhh... any. Use a towel then dip and rub it or you can fill up a spray can and just spray them. It doesn't take long for mineral deposits to melt under the might of acids. Please do not throw sulfuric or hydrochloric acid to your car. And if you do use the "free" route and you're male.. do it with style and aim properly. If you're practicing kegel, you might be able to spot-clean it per panel too.
Will cleaner waxes work?
Depends on how much cleaning power it has. But it generally does.
What are these cleaner waxes?
Also known as All-in-Ones, these are your "One Step" detailing products. They do everything at the fraction of the time and cost but won't do it as good as a dedicated step will give. The most accessible cleaner wax would probably be 3M's Cleaner Wax and Mother's Cleaner Wax. Since you're a Collinite junkie, Collinite has the SS lineup. Do you have Klasse's All-In-One (KAIO)? Then use that. That's an exceptionally great cleaner/sealant (more cleaner than sealant really)
Is leaving your car dirty for extended periods bad for your paint?
No. I haven't had my car washed for at least two weeks now mind you. It's so dirty that I just have to make it a priority to visit one tomorrow because the amount of dirt accumulating on the lower half of my door panel is mind boggling.
Will cleaner waxes strip off a layer of paint?
It won't do anything to your clear coat but expect it to remove your protection layer.
Will the alcohol and vinegar remove my wax/sealant protection layer?
Yes. IPA alcohol is often used as a wax remover.
Why is it on the roof and trunk?
Because these panels is where water "collects".
I have a wax/sealant layer, why do I have watermarks?
Your wax and sealant layer would increase surface tension of the paint so that water simply "rolls off" (sheeting) on inclined panels (for example, your doors and hood). But if the water stays on a level surface then it stays as it does on most sedan trunks.
Will a polish/compound work?
Hell yeah. In fact once you do a paint correction you can level the surface of the paint etch even if it's "in" your paint (because you're removing paint layers after all). So it fixes #1, #2, and #3.
How should I PM you next time?
I would have preferred a more humorous "HELP MEEEEEEEEEEE <thread link>" than just "<thread link>. And yes, you have to make the "me" extra long for more drama effect.
Hope that helps Cathy :naughty2: