Jason,
I have the exact same kit from last year. My answers:
1) I use the little grey applicator. It works just fine, and
P21S spreads sooooo easy that I've never bothered with anything else. Plus, it fits inside the jar, and won't scratch the surface.
2) I have used the little yellow sponge, but wasn't all that pleased with the performance. I still have it, but use some other wheel brushes.
3) The car wash is kind of strange. I thought their rate of mix was a bit high, so I experimented. I find that I can use about 1.5 capfuls in almost 2.5 gallons of water, and the mix is still good. While I think the P21S wash is a good one, I also use
Meguiar's Gold Class, which is a whole lot more economical at $8 a gallon!
4) The terry applicator is a good one....didn't scratch anything I've used it on.
5) The windshield wipes are a bit much. Since they are included in the pack, I did use them, but I wouldn't go out of my way to repurchase them.
hth,
DavidM