Just a couple of comments.
As for your friend chamfering the inside of his pistol cartridge cases.
Was he loading with lead bullets by any chance?
I had a friend show me that method when I was given a box of 200 rounds of lead boolits.
That method actually worked very well requiring no belling of the cases.
I prefer to use jacketed bullets since they can be run in my bullet feeder.
I bell the cartridges just enough to allow the bullet to go in easily.
As far as depriming before tumbling is concerned.
On one end of the spectrum you have those who do not tumble at all and on the other end of the spectrum you have those like myself who deprime first, wet tumble, dry, then polish their brass with Flitz or Nufinish to prolong the beautiful sheen.
There is no right or wrong way just a personal preference.