You are corrected...the Fender "safety tuners" (old name) do not have anything in the hole but darkness...there may be aother type of Fender locking tuner, but I am only aware of the style on the Jeff Beck or Strat-Plus strats, which has a large wheel on the back of the mechanism...but then, those look pretty much like a regular tuner (capstan with a hole).
There is a good explanation in Ritchie Fliegler's book (name escapes me, not the Amp one) with photos. That method is what I tried to describe previously. The wound strings shouldn't be any big deal, but the unwound can be fiddley, that is why I advised on the reverse wind to start (got this off the TDPRI website, years ago).