I've sent quite a few over as well.
I also think there's a lot to be said about guidance at the beginning. I've got an exceptionally long email that I send, covering everything from hardware explanations, links to refilling/cleaning videos, to vaping techniques, to juice strength and explanations of VG/PG (with repeated suggestions to drink a crap-ton of water), etc... One of the first people I referred mentioned feeling extremely dehydrated, at which point I realized that just handing them the card wasn't quite enough. Not everyone is as prone to doing hours of online research as I am