Sandblasting removed every speck of old paint and rust from the frame... including the hard to reach places (like where the chain tension adjusters screw into the dropouts). It also left a slightly rough (mechanically etched) surface which worked out great for filling in a couple of small dings and minor brazing gaps with JB Weld. I let the epoxy cure for a couple of days, then started hand sanding the frame to blend in the filler and smooth out the rough sandblasted surface. I've got some more sanding to do... then I'll spray it with a coat of self-etching primer.