[GiorgioE82]

VII. Clearcoat application.
Before doing anything else, make sure you have gloves, safety glasses and your respirator (and other needed PPE) on. You don’t want to ingest the clearcoat aerosol!!
In my case, like I mentioned, I used a 2k like clear coat provided by my local auto paint supply store. The process was the same as the Sp*****x2k clear mixing process. Remove the red plunger tip from the can’s lid, and use it to push the pin at the bottom of the can. There are plenty of videos on YouTube about this but my preferred way was to put the red piece on a level, sturdy surface, and then push down the can hard. Once the hardener is released into the clear inside the can, spend a good minute or two shaking the can. Find a piece of cardboard and spray a test pattern on the cardboard so you know what to expect.
Now, in fluid motions and overlapping each section by at least 50 percent, start applying a first coat of clear. It doesn’t have to be heavy. You just want to make sure you get decent initial coverage. Keep the can about 4-6 inches from the roof and work in side-to-side motions. Once you are done, set a timer for 15 minutes and go do something else.
After 15 minutes come back and do a second, heavier coat (check first that the initial layer is mostly dry to the touch). Remember to shake that can!!! Try to keep the application wet without letting it become so heavy that it runs. It’s tricky with the spray can but you’ll get the hang of it. Set a timer for 25-30 minutes.
Come back and inspect the 2nd coat to verify it has dried for the most part. I did 5 or 6 coats (can’t remember) to allow myself some wiggle room when doing subsequent wet sanding. After 5 or 6 coats, leave overnight to dry.
24 hours later
The clear should be super dry to the touch. Inspect the finish. If you are lucky and your conditions and technique allowed it, you should have a pretty decent finish without too many defects. More likely though, you’ll see several places where the clear has texture /roughness/orange peel and even some nibs or fisheyes. Not to worry, that’s where wet sanding comes in!
In my case, I had quite a bit of texture so I had to start with 800 grit as my first sanding step. Hopefully, yours won’t be that bad and you can get away with using 1000. Regardless, use your pump sprayer or spray bottle and spray a good amount of water on a section of the roof (I recommend one of the corners…maybe a 2 ft x 2 ft spot) which you will use as your test spot for your process. Go ahead and wetland with 1000 grit (DA polisher works great here; this is what I used) doing even passes. You should be able to see the light white milky froth of clearcoat being sanded away. Stop periodically, wipe the area with a microfiber towel and dry with the compressor to gauge your progress. You should start seeing a smooth, although dull and not shiny surface. If you see some fisheyes/pockets in the finish, my recommendation is to sand that spot carefully and specifically with a small piece of sandpaper and not the whole block or disc. At least to minimize its appearance.
Continue the process, this time with 2000 grit. Take the same considerations as before regarding inspecting often. Then continue the process with 3000 grit.
Compounding
Since besides being an electrical engineer, I also am a detailer, I own a ton of polishers. Hence, I pulled out one of my trusty DA polishers and a Rupes Yellow Wool pad to use in compounding. The good thing with the Rupes wool pads is that they run cooler than say microfiber or foam for a given effort. I used Menzerna 400 cutting compound for this stage.
Before compounding, go over your section with your alcohol or panel prep mix and a microfiber towel. Set your machine for a speed in its middle range (In my DA, I used midway between 3 and 4 setting) and start compounding. Go over your test section with overlapping passes, no more than a minute or a minute and a half depending on your compound and how fast it breaks down. Wipe off the compound residue and inspect the finish. You should see a marked improvement in shine from the 3000-grit step, even though the finish may be hazy.
For Polishing I used a red Oberk polishing pad with Koch Chemie Fine Polish. Follow the same steps as for the compounding in your test section. After wiping off the polish residue your finish should be quite glossy! Finish off by wiping the section with your alcohol mix/panel prep. Then move on to completing the rest of the roof.
Note: Once I moved to a larger section of roof after my test spot, I noticed that after the compounding stage the section was still quite dull. I took some time to rethink this and realized I had been too conservative in my 1k and 2k sanding and hadn’t removed enough clear. So, I made sure to redo that section and watch for the characteristic milky residue to show up before moving on to the next step. Once I did this, I was able to compound and polish and get a good finish.

See the pics below for the progression of wetsanding->compound->polish. I got asked by some friends what was the "stain" or defect in the pic after the polish stage;that's actually a reflection of a stain in my garage's ceiling!