Contacting for Thank You after Superday

Hi there,

Just wanted to ask about etiquette about how thank you notes should be done after a superday, I don't want any advice on the content of the note.

From my understanding, I will be speaking to a lot of people during superday. If I meet 15 people, should I follow up with a thank you for every single one? How would I even do that, is every person going to give me a business card? Do I write down all their names?

I thought it might be weird to ask them for their business card at the end, but I also found it might be weird to write down everybody's names after the interview. How would I know their last name/email anyway without a card?

On my last phone interview there were 2 guys and they just said their first names. I searched LinkedIn for them and I THINK I got them right. What do I do?

Also, I'm thinking about sending them an hour or two after the superday, this sound good?

Thanks.