Deck estimation: nothing beyond practices
Once coming to the card counting skill with hi-lo system, we need the parameter of the number of remaining deck to get the true count. There are some estimation by number of players, rounds dealt, and other factors, rather than by sight though I’ve never heard of that any player try to keep counting the actual number of dealt cards. Actually, the trouble is not worth the reward, since it needs more complicated mathematical calculation during the blackjack game.