I only have experience from drums on cars... But, I'm pretty sure it's supposed to be smooth. Even if it isn't, it will be after a few miles riding. It's the opposing pressure of the shoes against the drum that does the stopping... "smooth" doesn't make much difference as long as the drum and shoes are relatively clean. I just deglaze them every few weeks by doing one long stop with the rear brake, getting as close to "locking up" as I can without actually locking. I do the same to my Jeep E-brake.