The reason you haven't found a guide for breeding male-only Pokemon is that the process for breeding male-only Pokemon isn't much different than for any other Pokemon. The only difference is that if you want to not breed with Ditto, then you can't do that. But everybody breeds with Ditto anyway.
Unfortunately, there is no easy way to get a 6 IV Ditto, especially not in X/Y. The main two methods of getting a high IV Ditto in X/Y that don't involve trading are:
- PokeRadar chaining in the Pokemon Village, where Ditto can be found. Chaining guarantees encounters with at least three perfect IVs with a chain size of 61+. This guide will help. If you catch every Ditto after the 61st Pokemon, you can be confident in eventually getting a 4 IV Ditto at least.
- The Friend Safari, where all encounters are guaranteed at least two perfect IVs (but you can't use the PokeRadar). Ditto can be found in some Normal-type safaris via slot #3 (which makes things complicated, as you'll read in that Bulbapedia article). r/FriendSafari will maybe help you with this (read their FAQ), but it will be a very tedious process for a pretty average Ditto.
The best option if you're willing to trade is historically r/morebreedingdittos, but they don't seem to be active currently. You can maybe try their Discord (details in their FAQ). You can also try r/PokemonTrades or a different online trading forum, but you'll probably not have much luck asking for 6 IV Ditto in places like that (especially for Gen 6).
The option that's most likely to get results of some kind is PokeRadar chaining, so I'd go for that. If you can get a 4 IV Ditto, you'll probably be able to grind out a 5 IV Tauros with imperfect SpA after a few hours. Unfortunately, nothing comes easy with breeding Ditto, so you'll need to be very patient.
even with a five IV Ditto holding a destiny knot, it seems to me that I'd still have to rely on luck in order to hatch the optimal Tauros
That's right. You can't guarantee hatching a 5 IV or 6 IV Pokemon. If you want to breed a competitive standard Pokemon, you will have to hatch lots of eggs and replace the parent as you described.