at some of the shops I worked in we had a seattube reamer (three cutters) and type of flex hone that worked wonders. it was an odd kind of bottle brush looking nthing but had about 1/4 grit or pumice balls at the ends of the bristles. it was somewhat mandatory to always use that a new frame.
__________________
“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk