Optimum opti-seal is an excellent polymer sealant similar in application method to UPGP.
I took the following directions from my method of applying UPGP and slightly tweaked it. It should apply to OS as well.
1.-Shake the bottle.
2.-Take a clean microfiber applicator and spray 1 spray onto it to prime it.
3.-Spray it once more and do about a 3 SQ FT area.
4.-Apply in circular motions just making sure to overlap and cover the entire area. You are not polishing so no need to rub too hard or over and over. I always finish with straight lines from front to back of the panel. 3 SQ FT is an estimate. Another thing to look for is that your applicator is no longer leaving anything on the paint. But on certain colors and without really good lighting its sometimes hard to tell anyway. I basically make sure I do about 3 SQ FT. Then I'll wipe over to the side a bit where I know I haven't applied any to see if there is still anything coming off the pad. Fred gave me a tip that is a great idea. When you are no longer sure if anything is on the pad touch your clean window with it and you'll be able to see if there is still product on the applicator.
5.-If I don't see anything then its time for (1) more spritz to the applicator.
6.-Repeat until you get to the last panel. Now just walk away. Their may or may not be a slight film on the paint for a bit but it starts it's bonding process immediately. Now just do not touch
Even though on some colors in some lighting it seems like you aren't putting anything on your paint just TRUST the product. It will come out great if you don't over apply. I didn't have any trouble at all even the first time but I have read some people apply too much. It is a little disconcerting not always being able to tell if you are putting anything on your paint.
I haven't tested OS enough with layering to know but based on my experience with UPGP I would recommend more than 1 coat for maximum gloss and beauty.
A second coat can be applied after the necessary cure time. Typically the cure time for polymer sealants is 8-12 hours.
With UPGP you can layer after only 45 minutes but I'm not sure what the rule is with Optiseal. A search on the optimum forum would reveal that to you I'm sure.