Unless VERY dirty, I always used my car shampoo and a boars hair brush to wash. For the hard to clean areas, I'll use an All Purpose Cleaner like Adams APC. For protection you want to make sure the product is water repellant, silicon free so it doesn't attract dirt, and has an SPF so it actually protects the surface.
303 has all these but the water repellency and is a good product, but once it rains, it's gone!
Most OTC products contain Silicon or other products like alcohol that dry out vinyl and plastic (armor all is the most commonly known) Silicon is like a dust sponge! Have you ever seen brown tires? 10-1 it's because they use a silicon product.
There are products out there that meet all the criteria I like to meet.
Adams (forum sponsor) has SVRT which works on Vinyl Rubber and Plastic trim. You'd put it on, let it sit so the vinyl can soak up some LOVE, and then after a bit (more time is better) you'll level it off with a dry towel to fill in the low spots and cut down the high spots. If left too thick, water will make the excess run off on your paint. While it won't harm your paint in any way, it looks bad after it dries.
So, SVRT if you want long water repellency, an SPF, and silicon free.
Give it a try, I PROMISE you'll love it. 110% guarantee means they pay YOU to send it back if you're not impressed. What do you have to lose?