Looks like some of the pits are a bit deep for the scotchbrite to get out. You might start with 220 sand paper, then work to 400, 600, then all the way down to 2,000 and then more scotchbrite. after the scotchbrite, you can use some rubbing compound and then an aluminum wheel polish (like "Mothers") to polish it up. Yes, you can paint the vacuum canister.
If you have a buffing wheel on a bench grinder, you can buff the distributor to save time doing it by hand.