My motorhome has rubber seals around the windshield, and windows. It gets a similar look where the water runs over them.
This is a long shot in the dark, but if that is what it is spray a product called "black streak eliminator" onto it then wash with your regular car wash. Duragloss makes the...
Here's another good AG link. When you get on scroll down to select catagories.
Auto Detailing Facts, auto detailing Tips, How to detailing Guides, how to polish, how to wax, DIY detailing, do it yourself guides
A few years ago AG had a Christmas package of wash bucket; grit guard; mitt; shampoo that I got for my son-in-laws. They liked it. To be honest I don't remember the cost.
Foam=I use terry towel + finger tip pressure while on.
Wool= I use the spur while spinning. Son-in -law, who had a detailing business, uses tip of screw driver.
These deep reach brushes fit in the tightest wells, plus I like them on wheel barrels.
Wheel brushes for spoke wheels, deep set spoke wheel brush, large wheel brush, wheel brushes
Plus, I'm with killr on easy to maintain with sprays of ARO.
Malls; hair salons; medical buildings; go door to door checking to see what employees (car there all day). Golf clubs cars are there 4+ hours so you will find plenty of business if permissible (usually is, especially if you give those in charge a good rate).
Waterless wash is necessary at these apartments I'm at. To be honest I think they do induce a few swirls. After almost three months of WW my cars are probably where they are at my annual major detail. No biggie, it's just another opportunity to :buffing:
It's rare that we will be below freezing all day. Here is what I've been doing for three months, and will continue through winter. Wash at the spray wash with "rinse" setting only (no soap). Drive back to the apartment. Most of the water is gone, but some remains. Waterless wash, and dry.