when we had housemates, it was largely a matter of waiting until they were out of the house, using quiet implements, and playing music to give ourselves the illusion that sounds would be masked. now that it's just the two of us, we go through the same routine, since we live in an apartment and the rooms are either right at the front of the building, with a thin door through which sound carries easily, or right off the air shaft, where anything our neighbors say or do reverberates, and we have to accept the same is probably true for us.
less about ttwd, but back when my brother was living with us, most of the spankings took place at play parties, which works well, although w has joked that she thought we were one of the few couples that went to a play party in order to get privacy.
as for the loopy thing, you don't have to buy it: many of us around here have made them for ourselves, using either stuff from around the house or from the dollar store. but be warned: those things are viciously painful and incredibly quiet.