Very well written question.
The easist way to accomplish your pontoon polishing project would be to order a kit from a company called metalwax. You can access their site by putting a "dot-com" after "metalwax". They have a bottle of cleaner and a bottle of polish that will work on your pontoons. Don't buy the optional spray cans - they will be almost useless for your application.
Your pontoons are a low grade aluminum. You will get them shiny, but don't expect perfect brilliant mirrors when your finished.
I have nothing to do with the company that sells metalwax. I stumbled across the site while I was searching for a polish to use on my aluminum canoe. Surprisingly enough, the stuff actually worked!