I am pleased to see that you were taking notes!
Doubling white wires at the neutral/ground wires would be functional, but when it comes to electrical work: stick to code as much as possible. When your hut goes up in flames, you don't want the insurance company weaseling out of paying you because of a couple of code violations.

when you do run a new circuit, always remember that,
per code
, although you can double up a couple of equipment ground wires at the neutral/ground bar in the panel, at the neutral/ground bar,
each white neutral wire has to stand alone!