Ordinarily, you'd need to breed both Egg moves and IVs together at the same time to produce better parents for passing down the IVs, egg moves and nature you want. This is fairly simple: if you don't include Pokemon with a sufficient amount of perfect IVs, the baby won't have good IVs and won't make a better parent than the parents you already have. If you don't include Egg moves, the baby obviously won't have the Egg moves you want, so it won't work well as a parent. However, if the two parents you choose collectively have good amount of perfect IVs and the Egg moves you like, the baby will have both of these traits, essentially making it a two-in-one and thus a more useful parent. There is no point in breeding like this if the offspring you get don't make better parents than you already have, because then you get absolutely nowhere.
However, your 6 IV Ditto changes everything, and basically means you can focus on Egg moves first and save IVs for later. Obviously, there's nothing wrong with adding IVs into the mix if you can, but it's completely fine if you can't. For your exact situation, this is the process I'd follow:
- Find two parents for the baby. These parents don't have to have good IVs, as your initial IV source will be your Ditto later on. (It'd obviously be good if the parents have some perfect IVs, as this can speed up the process. However, this is by no means a necessity as mentioned.) The only criteria you have to meet is that your selection of parents will give the baby the desired egg moves, and that the female will pass down the species you want. If one of the parents has the nature you'd like for the baby, have it hold an Everstone so it will pass it down to the baby.
- Repeatedly hatch Eggs until you get one with the nature you'd like for your Pokemon. Verify that this Pokemon has the Egg moves you want. Once this is done, equip it with an Everstone so it will pass down the nature you want.
- Once you have obtained the Pokemon in step two, pair it with your 6 IV Ditto. Equip the Ditto with a Destiny Knot so it can pass down some of its IVs. Keep breeding these two Pokemon and hatching Eggs.
- Once you hatch a Pokemon with better IVs than Ditto's current partner, replace Ditto's partner with that Pokemon for a higher chance of passing down perfect IVs. Remember to move the Everstone to the new parent so you can pass down the nature you want. Breed these two Pokemon together.
- Repeat step four until the hatched Pokemon has perfect IVs. Ditto's partner will always pass down the nature and egg moves you want to the offspring.
Without a 6 IV Ditto, you'd have to follow a process like the one here, except the initial parents you choose would have to have the desired Egg moves as well as good IVs to pass down with Destiny Knot or Power items. As you can see, the 6 IV Ditto makes breeding competitive Pokemon far more simple than it normally is.