they got those 10$ sets of carbide burrs on fleabay. they RUUUUUULE.
i feel like the nikasil gets out of my way pretty easy. chamfering kinda helps it "get nice" too.
the alloy cylinders go away real fast with the carbide burrs on "10." i like to start with my dremel on low, then slowly gain confidence with it, turn it up slowly, until you climb-cut out on to a mating surface, then turn it back down....
since i started porting stuff, i pretty much just go big on exhaust ports. not too big, more width, i'm quite pleased with the results. no need to push it too far in my case.