MikesJo, have you read the Autopia Bible? It's David's e-book, available at the bottom of the Autopia homepage. It'll probably help you with lots of the basic concepts as well as specific techniques. It's sorta the indoctrination most newcomers need.
Long before you think about Zaino vs. S100, you need to focus your attention on surface preparation. Most of us begin with a careful wash, claying, then polish/glaze to be sure the surface is truly clean and free of scratches and other defects. Only then do you move on to the decision about whether to use a sealant and wax, or just a sealant, or just a wax.
I may be
way off base here ... but ... I'm just a tad curious about your saying the paint's in good condition. I have a classic car and when I found Autopia, I thought the paint was in tip-top condition. But then I clayed it -- just 'cause lots of Autopians said it was The Thing To Do -- and
zounds! then I discovered what a car's finish is supposed to feel like. [My little eureka experience is covered in
this thread.]
Take your time. Don't rush into this. If you decide to apply a sealant like Zaino, it'll be harder to go back and deal with the surface-prep issues. (In fact, some of the high-quality sealants seem to magnify any remaining defects in the paint finish. If you choose a wax instead of a sealant, that's not so much a concern.) So ... work on prep first. Then, when you get around to applying a sealant and/or wax, that'll be just the icing on the cake. Perfection isn't built in a day. :up