You can polish up both mast and boom but the shine will quickly fade as the aluminum oxidizes. The oxidation actually protects the aluminum, but is unsightly and comes off black to your hand. The only way to preserve the look is to have it re-anodized. The various clear coats available flake off under use and you end up with even more of a project fixing it next time.
I painted mine with Interlux Perfection. I chose white, but there is a wide selection of colors. Clean the aluminum up using wet/dry paper removing all of the remaining coating and oxidation. Wipe down with acetone a couple of times and then prime with zinc chromate primer. Perfection is a two part epoxy paint and, if used, read and follow the directions carefully. Especially the recoating times so that each coat will bond to the previous one. If you select Perfection I would recommend using a very short nap roller, similar to one used for rolling epoxy resin, and put the coats on lightly. Too heavy and you'll have a running mess you'll never get right until you sand it off. Spraying would be ideal, but requires a fresh air or self-contained breathing apparatus due to the cyanide in the paint. Roll and tip works fine.
The only thing I would have done differently on mine was I probably would have etched the aluminum better with phosphoric acid prior to priming. Read about that about a week after completion of the job. The paint seems to be holding up fine after 1 year and it looks great. I hate the look of aluminum, even shiny, and so this was on my list to do for some time.
btw, mine is a Cal 21'.
Also I recommend Don Casey's latest book, Complete Illustrated Sailboat Maintenance Manual. You can find it at amazon for less than west marine, and it's quite good on these projects. He discusses this job in the book-good ideas on how to hang the mast while painting.