Re: Descending at vmo
What I used to do was to descend in V/S until just below Vmo/Mmo and then switch to IAS mode to ensure we didn't overspeed. Similarly in the climb, used a comfortable V/S until a suitable point and then use IAS at the speed I didn't want to go below.
Sounding the overspeed clacker/horn/whatever demonstrates a lack of sufficient scanning/monitoring, IMHO.
On some aircraft (the ATR being one I've noticed most) there is a fairly constant difference between the Captain's and F/O's ASI's. If taking the speed to close to Vmo/Mmo this needs to be remembered. On the ATR the Captain's is normally the higher, and the Overspeed horn is linked to this, so it is incumbent on the F/O (if he is PF) to make allowance for the difference.