Best to not learn how to do anything via YouTube. Anybody with internet access can post anything there.
Go here.
http://www.quarterbore.com/library/a...00trigger.html
"...scrape away some kind of a sealant..." Said sealant is there because Remington is terrified you might sue them if you mess it up.
"...let a shot go on bolt closing..." Happens when the trigger is adjusted to be far too light.