The parents are very important. Exactly three IVs are inherited from the parents and the rest are from IV frame 8 (you're right on track with using the capture tab). When you find a seed and PID frame for breeding, the IVs will look something like this: "Ma, , Fe, , Ma, "
The "Ma" shows inheritance from the male parent. In this example the baby would inherit the HP and SpDef IVs from the father. And of course "Fe" is the female parent, and in the example the baby inherits the Def IV from the mother. The blank spaces are taken from IV frame 8 - say in Time Finder you find a seed with IVs of 4, 31, 5, 31, 6, 0. In this example the baby is given a 31 in Attack, 31 in SpAttack, and 0 in Speed.
So you can see that without 3 flawless IVs between the parents, breeding a flawless Pokemon is impossible. In theory it's easier to execute a capture with your desired IVs. However you miss out on a few things - egg moves, DW abilites, Pokemon that can't be captured in Unova, and having it at level 1. The Ferroseed you brought up could be achieved by having a flawless father, finding an IV frame 8 of x,x,x,31,31,0, and finding a PID frame that shows "Ma,Ma,Ma, , , ".