If I am using nitro powder loads I clean with Hoppes and a copper wire brush. Then a light oiling.

If I have been using BP I usually start the cleaning at the range by putting a couple of patches down each bore that has been soaked in a BP solvent. I finish with hot soapy water and a final rinse with clean boiling water, dry completely then oil.
I usually limit the shooting to 20 rounds or less so there isn't a great deal of build up.