I use a lodge 10.25", I wish I had got the high walled version to contain splatter and so it could double as a dutch oven. I also have a rough Chinese 12" that I'm waiting for a rainy day to sand down. Cast iron is the best.
DayboSupposedly sanding cast iron is a bad idea because it "closes up the pores" or something, although I don't get how machining wouldn't do the same thing - then again, I am not a metalworking expert.
zappdustI ended up chucking it and buying a 12" lodge because I couldn't find anything tough enough to bite into it, but soft enough to polish it. I doubt it would close the pores as they're microscopic and unless you're using japanese waterstones, it'll never be perfectly smooth to that degree. Loving my lodge though! I bought a 3 ring burner for car camping and hiking.
zappdustThe bottom would be the surface to sand/grind/machine for better heat transfer on an electric stove IMO. Also I'm a machinist ;-)
I wouldn't worry about porosity of the cast iron, it'll be fine. If one is so inclined to be worried, sanding with oil (probably want to use something edible) would do a better job of preventing grit build-up.
Daybotry using salt and a lot of heat ,its called proving your pan .This was done before the days of nonstick variants.
Warning this process is only for cast iron pans,be careful salt gets very hot and stays that way for some time.