Dan:

Assuming you are dealing with bare wood, I would strongly suggest you to start fairing the surface with a razor sharp low angle hand plane. You will get rid of those bumps and imperfections in a matter of minutes. Watch out the grain orientation, OK?

Then, start the 80 / 120 / 150 / 180 / 220 grit series of sanding passes. You'll get an incredible smooth finish with almost no effort.

Hope this helps.

Marcelo