what you have for a polisher will work fine for now, but I would suggest a Porter Cable in the future. The only thing you really can't do with what you have, is correct swirls/scratches very well. You will, but not completely. Stick with what you have for now, and save $ for the Porter Cable.
As for under hood detail. What I do is a 50/50 mix of Simple Green, if I have some tough grease, I use paint brushes to get down in the tight areas. Rinse off with water. Then take a touchless tire shine, spray all over the engine, close hood and wait 15 minutes. Come back and wipe off any excess residue. It works really nice, and will speed up the cleaning process in the future.
You will get different techniques from everyone. My suggestions may not be the best, but they work for me.
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