It's not pointless if you've a cam or some other mild mods. On a stock motor, it probably helps a bit, but it'll mostly just move the powerband up more than add to the overall power. And free up some high-RPM, say over 4700.
As far as polishing the runners, yeah, it's the same process for polishing anything made of aluminum. Typically, polishing machined aluminum (like fuel rails) is much easier than cast aluminum (pretty much everything else on the TPI). The only thing is that those runners are so odd shaped and hard to work with, it's a pain in the *** to polish.
Here's a pic of my runners before and after. I only mirror-polished the upper flange. Everything else I just hit with some steel-wool and Mother's Aluminum & Mag Polish. It's not as good as a full polish with sandpaper et al, but it sure was a lot easier. I also didn't want to do all that work if I was going to upgrade the runners soon anyway.
