I was turned on to the Zep product about four years ago - at that time, Lowes sold the matching formulation with a brand called "Red Max Pro", or RMP as it's called in the forums. RMP/Zep works best on "older" fiberglass and some painted metal. It is NOT a wax, you can't think of it like that. The best way to think of it is as "liquid plastic". Here's what I've picked up:
Prep is very important. The more virgin you can get your surface, the better Zep will look, otherwise you'll just end up with very shiny dirt. Apply very lightly. Let dry between coats. 4-5 coats seems optimal.
Test on decals - some are fine, others not so much.
There are two ZEP formulations - High Traffic, and Wet Look. I think you want the Wet Look formula. I still have three gallons of my RMP left over so I don't use Zep.
Remember, RMP/Zep is a FLOOR finish. Its UV protection is probably minimal, since most kitchens don't get direct sunlight. Apply it with a spray bottle onto a white microfiber towel, and wear disposable gloves, unless you like the look of clear nail polish.
A segment of the boating community has used RMP/Zep for years. When Lowes discontinued the RMP brand line a couple of years ago, I bought four gallons as a store house. There is some question as to whether the Zep Wet Look is the same exact product as the RMP #3 formulation, as users of Zep have reported some peeling and flaking a couple of years after application. I have only ever used RMP on my buggy, and have not noticed flaking/peeling.
Also, RMP/Zep seems to be sensitive to some cleaning products, such as Simple Green and Purple Power. It may be best to wash ONLY with plain water, or a VERY VERY diluted solution using SG or PP or a similar wash.
I basically apply a coat or two each spring, after a good wash down.
Do not use on Rubber.
Do not use on automotive type clear coat finishes.
To reiterate, you MUST get all the old wax and polish off before you apply. There is a Zep stripper that you can use as well but it's probably not as easy to use, as its designed to be applied and let sit on a floor, and would tend to run down the sides of a vertical application.
I don't think I'd use it on a rubber roof.
Some have used it on glass and reported good results, others have reported streaks and smears. Again, it probably depends on the surface. If you use a product like RainX on your glass, it may not take to RMP/Zep very well.
Here are some of my before/afters.
Always remember, you're a unique individual - just like the other 7 billion people on the planet...