Do you hold the block signal until after the try has been completed?
 

I find myself holding my block signal until after the try has been completed in order to signal whether the basket counts or not. Is this correct mechanics or should I immediately signal a block and then signal if the basket counted afterwards? For PC fouls, I immediately show my signal.

Have a patient whistle, and a patient signal.

I give all my signals when I have made a ruling. I do not hold or try to be quick when not necessary. Kind of why you wait and have a patient whistle to see the entire play, because you might rule that nothing was needed to be called.

Peace

I do whatever feels right for a given play.

If I feel I need to sell/communicate the block first, I'll give that first and then afterwards count the basket.

If you give the signal for counting the hoop, everyone knows you have ruled a block. I just about never signal block on a shooting foul ... at all. If I identify a shooter and we end up with free throws, everyone knows I didn't go PC.