As a young boy, I always washed and scrubbed my cast iron skillet after cooking. This was usually done with the help of a SOS pad. I sure as heck don't do it that now. It's a hot water only, rinse and a scrub
with a brush. If there are nasties still stuck, I scrape them off using a plastic Lodge scraper or a scrubbie. Then it goes onto a gas burner to dry and heat up. A very thin coating of oil is applied then wiped off.
The oil can't be wiped off 100% so a very thin coat remains. Any thing more than a very thin coating of oil has a chance of going rancid and/or turning gummy. Over time this helps develop a good layer of
tough seasoning. Seasoning is a build up of oil and very fine food particles that develops only with age. It can not be rushed..To me, seasoning adds flavour. That is why some die hard C I cooks have dedicated
cookware, that is a vessel to cook only one thing in so the flavour carries on.... As far as fine food particles being part of the seasoning and possibly harbouring bacteria or other sickness causing organisms,
they won't survive the intense heat of a cook..