Okay, question from someone who never bothered to EV train in the past, but wants to learn. This guide was very illuminating as to how fast horde training can be, which was a big part of me deciding that I'm actually going to bother with it, but it also seems a bit dated as it states that males can't pass down HA during breeding, which we know isn't true, and it's also not exactly clear on certain points. On to the questions:

1. If my lead pokemon had and is cured of pokerus, it should still double the IV take for the whole team correct? Or do I need to infect every mon with pokerus for the doubling to occur?

2. Do I only need to equip a power item to the lead pokemon to get the +4 EVs, or do I need to equip one on each member of my team?

If it's literally as simple as having a lead with pokerus/cured of pokerus equipped with a power item to get 50 EVs in one turn from a horde then that is insanely easy.