i love Poli-Seal. it's so underrated. no dust, no residue, etc. you only have to use a tiny amount to get the job done.
i mostly use it nowadays for coating upkeep. for instance, a Mini Cooper GP that is coated and has spots in the hood valleys from water sitting - Poli-Seal cleans it up perfectly.
it's also great on glass, coated with Opti-Glass or not. by hand or with a DA and finishing pad, it removes light water spotting with minimal effort. same with glossy trim.
the one thing to keep in mind is Dr G a while back said the sealant component is pretty robust, so it's not something you want prior to coating. thus, i'm not entirely sure how well it works as a base for another LSP. i don't know how you'd accurately test that because if you top it, and it's still exhibiting protection in a few months, is that the included sealant or the topper?
the claim is "months" of protection so i don't know.