observations about throwing big pots

I like to throw big, but as yet I'm still self-taught and
what I am doing is throwing them in one go and using porcelain.
This is difficult, I find. I tend to throw thin and a large
porcelain piece doesn't like that, no matter how much I dry it
with a metal scraper. Nevertheless I've gotten acceptable (not super)
results.

However yesterday I was watching someone throw a large pot
and I noticed that he took it off the wheel after he made
a cylinder, used a sponge to dry it, and let it sit for maybe
10 minutes.

Furthermore the way he threw it was something I've seen
before but as yet have no explanation of: he didn't make
the sides smooth as I do, but he gave it a corrugated look.
Hence his inability to use the metal scraper to drying.

He then did something odd: he covered it with
plastic as if it were completed, and left it overnight.

I don't know what clay he was using, but it didn't look
like porcelain.