So how exactly does a female pass an egg move?

Say I wanted a Ferroseed to have Leech Seed and Sneaky Pebbles. So I breed one with an Onix that has the move to pass it on. Now, I get my Venusaur with Leech Seed to pass onto another babby Ferroseed. Now I have two Ferroseeds with each move. What's the next step?

Also, is it possible to pass on more than 2 egg moves? I've been seeing giveaways with people claiming that they have Tyrunts with Dragon Dance + 3 Elemental Fangs. Is this connected to the whole females can pass on egg moves situation?

Spikes would be nice in conjunction with Stealth Rock and Leech Seed