additional layers of Hyper Seal will ensure complete coverage, may add gloss, and can modestly increase durability. Some add Wax for that reason, like the carnauba shine. Added coats will not equal the benefits of ceramic - OCP is SiC, not Si02 and Gloss Coat is a hybrid of both chemistries.
if you chemically decontaminate (not clay) it's very possible your Gloss-Coat is still there and performing. You can layer coatings but it doesn't extend the durability. Polishing and re-coating starts the coating clock at Day One.
Mr Outback, I was not sure what you were asking - Optimum ONR will not have more gloss/slickness than OC. OCP+ can stand up to clay IF you use a great lube we recommend Wax) and are careful. Clay should not remove OCP+, so marring is the concern. We recommend chemical decontamination on ceramics...and suspect most clay is overdone.
Opti-Glass is formulated to cope with wiper abrasion and Opti-Coat Pro is not - OCP will only last a few months in glass, depending on weather. There are chemical similarities but performance differences.