It's not necessary to signal every decision - which I've used a few times as an excuse to wait for the player reaction!Agreed. For the flick of a defender you're giving the decision straight away. It's not a hard sell.
If you wait for the reaction of the players a couple of times then that brings its own problems, although there's certainly times you can do this.
Ball goes out and you're not sure who it's come off? Wait and see who goes to get the ball or where the other players set up. And if someone then objects, just give the signal that goes along with the majority and say "Oh sorry, I thought it was obvious: Blue throw".