There is a lot of good advice in this thread.
Here is mine.
If you are working with pistol cases, tumble them with the primers still installed in a standard vibratory tumbler. De-cap and size at the same time. The final product will shoot just as well at 25 yards or less.
The primer pockets do not need to be cleaned.
They do need to be dry. If you are using a wet system, then yes, you will need to de-cap the cases first.
Good point. I wet tumble so I decap first, but if I dry tumbled thats how I would do it. I wouldn't worry about clean primer pockets.