Can you use top coat over ceramic as "maintenance"? or is useless? Something better?

You can use almost anything on top of a coated car...wax, sealant, quick detailer, etc.... but you will be covering up the characteristics of the coating with anything you apply.

Most coating manufacturers have created their own spray sealant that they recommend using on top of their coatings for various reasons...

CarPro Reload
22ple VS1
GTechniq C2
Gyeon Cure

etc.

I do not like GTechniq C2. Its dries streaky and looks terrible.

Check out Sonax Polimer Netshield, I really like the stuff.

You could be using too much product or the paint is too warm when you're applying.

From the list Zach posted, I like gyeon cure a lot, but I haven't tried them all. Lately I've been putting Carpro Hydro2 on everything because it's the fastest.

Polymer net shield is a good product, but I wouldn't put it over a coating.

I have tried all of the products I had listed in my previous post, and I have had some streaking issues with all of them at one point or another. In 98% of cases, I have no issues with any of them and really enjoy them. GTechniq C2 is one that I use quite often and rarely have issues. If you use too much product, wait too long to wipe, work in too warm or too cold of an environment, etc. you may experience finicky behavior. All you need is one light spray per section (1-2 sprays total per average sized panel, such as a door).

No, the car was ice cold. I just pulled out of the garage into shade - about 10 feet to wash it. Prior use was the night before. Air temp, 68. I thought it was very strange. I was using new MF towels, not sure if that had anything to do with it.

If you had used a shampoo that leaves some sort of gloss enhancer, wax, or anything else on the surface, it might interfere with other products such as these spray sealants. That has always been my suspicious as to what may be the cause my streaking issues from time to time.

I use Optimum wash, which I've always used. I've used C2 plenty before and never noticed any streaking. Im thinking it might be temp related.

What about reload?

.... what about it?