A couple of months on from my first post here,
I used Bill's Eevee and a Ditto to produce two eggs, one of which became an Espeon and the other a Jolteon.
I've brought the latter to level 70 by now; he apparently has a relatively good IV total and knows Thunderbolt, Iron Tail, Helping Hand and Double Team. I've always put off having a Jolteon again since I used one in Red or Blue (if not both games; it was always my favourite one) and want to set myself onto using other things, but I can't help but come back to first gens, and it's great having him on my team.