Harbor Freight and many places make soft wheels that go on a drill as far as polishing inside the holes.. if I need to sand I use a dremel and a small brass wheel.. works great and then I use 0000 steel wool before I polish..
Maintenance is key to a long lasting shine… washing it once a week with no grease ph balanced soap helps a ton! Using degreaser to loosen up dirt every so often is fine. Just make sure you rinse quickly… If you’re in an area with salty roads or run in a lot of lime stone rinsing it as soon as possible makes a huge difference as well… no need to wash it everyday just rinsing is enough, the less time the elements are on you’re aluminum the better! Aside from that using Liquid Metal polishing every month or two can prolong the shine as well. Hope this helps Thanks for watching!