Assuming one has a fairly straight approx 4.5" OD x 10" long round
motor with smooth surface, what would be a good way to get some heat
sink type of deal ?

I am thinking about

A) getting say 3/8 or 1/2 alum channel, cutting it into pieces the
length of the motor and attaching the "strips" flat bottom toward the
motor around the circumference. 3-4 zip-ties holding the Us against
the motor

B) doing something with copper or alum sticky foil, where you create
as many folds as possible in a "pleaded" fashion - infinitely messier
affair, but would it be more efficient in dissipating the heat ?