Really wasn’t thinking about knurling the drum, the shoes looks to be made out of M series steel which is hard, and has a very fine grain that doesn’t gaul up in large chunks. Normally used in aviation bearings. The material will take a knurl easier than it will filling. Not excessively deep but, may or may not help create a more consistent mating surface with the relatively soft material of the drum.
Now, that being said, I’m probably not gonna try it.....Not worth pissin off the tech guy.....