On our old 146 you can lock the VS, lock the IAS or lock the altitude. You can also capture a selected altitude, but for CDA, all we can do is now take our little booklet supplied by Gatwick (thanks Claire) and look at the chart on the back to get a fpm from the range/altitude.
Remembering to fly level for 20 seconds first is a problem as we get bored by then, but trying to keep a speed and VS is a nightmare as the old autopilot is very poor at locking on and holding a VS. The RJ is supposed to be better, but they never let us fly those and now never will (BACON!!).
Generally, it would be a lot easier if ATC gave us a couple more range checks along the way, as our -100, G-MABR, doesn't even have a nav system that helps at all. Others with GNX-XLS fitted can help if the pilot is clever enough to put a couple of self generated waypoints in, but that takes time and familiarity.
There are times when 500fpm will result in a level segment so you simply cannot win. However we do try our best!
Also, can the ATC on director please tell us to reduce to 160kts before we capture the glide, not just after! it's a lot easier especially if we are just leveling at the capture altitude.