I've just tried the P21S wheel cleaner gel on my painted wheels for the first time and have a question about how to use it.

I followed the instructions and sprayed it on the wheel and let it sit for 10 minutes, but it dried up. Does it still work while being dry? It says to let it sit on the wheel for up to 2 hours! Is that right? Do I have to wet it occasionally?

How does it work?

Thanks for your help!