CONF iture
There are quiet a few things that you don't understand correctly and I am not an airbus pilot is just another one of them. I have flown not one but three airbuses. So you won't get anything out of that.
Select speed the target is on FCU. But normally when in managed one glance at bottom of speed tape you can confirm app. activation. However if you like a longer way or that's the way your company does it I have no problem with it. That does not make it compulsory for others.
Cak, the issue at hand is only approach activation and confirmation so I am not going to comment on the descent and conduct of the approach. Some would activate first, confirm and then use select speed till required. There is another document on effective use of FMS. where you can create altitude constraints for better control of managed descent and approach. But I am not entering into it.