Dave,
On the pitted areas, a fine file can be used to help remove metal a little more quickly.Be careful not to concentrate on one small area, but feather the file work somewhat, so as not to create flat spots. Generally speaking, some shallow pitting will wind up fairly well hidden by the blueing process. Don't take the word,"blueing" seriously, the end result is black, which is why the Brits refer to this process as "hand blacking".
Sand away, when working by hand, you'll wear out before the barrel walls get thin.
Jim
