In my experience, once you've got 'em, you've got 'em. In my yard, you can't kill them, so I'd say it doesn't matter what you do. I'm sure that's not technically the correct answer, but since my Crocosmia shoot flowers over my head every year, I'd say I'm doing fine. LOL!

I don't think you need to the foliage off. You will find they multiply and self seed a lot, so you'll have plenty by next year.