It's definitely a topical treatment, no matter what the packaging says, and I didn't do any surface prep other than a simple wash with a plastic-netted sponge. I did have streaking after my first application, but that's because it started sprinkling before I could finish. A good wash and second coat later and it looks great. (Btw, the TS-1 packaging doesn't mention any such elaborate surface prep process.)
A note on price: one of the guys in the AV forum quotes a price of something like $21/towel, but that's not accurate (at least as I understand what he means by "towel"). A box of 6 pads was $40 shipped, and it takes 2 to do all of our cladding in a nice thick coat. That's not exactly cheap, but if it lasts 2-3 months as advertised I figure you get nice looking cladding with minimal maintenance for about $50 a year.