UPDATE: So, for anyone who also wanted to know the answers to these questions:

1. I ended up eyeballing the amount. Imagine an amount the size of a pea, then split that amount in half. That’s how much I used, and it worked fine.

2. The paste (I used K5-Pro as recommended) is quite thick and sticky and difficult to get to behave the way you want, so I ended up just doing the “middle dot” method and spreading it a bit with a popsicle stick before smushing it the rest of the way down with the heat sink. Seems to have done the trick.

Good luck!

(1) Exactly how much thermal paste should be applied to the CPU?

(2) Which application method should be used? The linked instructions list four methods (vertical line, horizontal line, middle dot, or surface spread) but it’s not clear to me which one is appropriate for the Switch. Thanks!