Hey Zach!
As has been mentioned previously, Flitz is a great metal polish, but it's also advertised as a protectant. I've used Flitz, as well as Blue Magic Metal Polish Cream (which is also advertised as a protectant), many times on the insides of lug casings. A fellow VDF member recommended Blue Magic a few years back, saying that it actually penetrates into the pores of the metal to protect it. I don't have any information that can back up that claim, but for that reason, I have applied it to the inside of my lug casings with a Q-tip, then I use an old rag or strip of an old cotton T-shirt to wipe it clean. I figure the residue left behind will protect the inside of the lug.
That's what I do, but I certainly wouldn't try to dissuade you from taking the extra step of waxing the inside. I just figure I've spent enough time disassembling the drum(s) and polishing all the little parts to take the extra time to apply wax...but again, that's just me. :2Cents:
Oh yeah, wrapping your lug springs with felt, which has also been mentioned, is a great idea as well. I've gotten birthday card-sized rectangles of felt in an off-white color that seems to match the old stuff perfectly from Hobby Lobby for about $1.00, if I remember correctly.
I hope this helps, and good luck!
Lynn