Peter's instructions are spot on. 1 & 2 might work. 3 WILL work even
if the problem is frozen cables or other parts of the mechanism, but
then you'll have to readjust the brakes to make them servicable for
driving. At least it should allow you to remove the drum for access to
the brake. I'm not sure it's corrosion in the brake mechanism that's
the problem so much as the shoes seizing/rusting to the drum over time
due to moisture. After too many first-flight-of-the-year sessions like
this, I no longer set the parking brake for long-term storage.

Chip Bearden (with experience on both Komet and Cobra trailers)
ASW 24 "JB"
USA