Either:
A. Submerge the entire frame and fork in an Oxalic bath and the use a automotice brake hone in the seat and steerer tubes to fine tune them or:
B. Use a rounded file to clean up the inside of the seat and steerer tubes and then use the hone or:
C. Use file only
C. Use the hone only
The method you choose is dependant on how deep you want to get inot the job