Disagree a bit Notso F.
In my opinion a CDA approach is an idle descent without a level segment.
So : one flys it as a glider,
which means speed is a pitch mode ! (and thrust is at idle)
So don't fly them in V/S because then speed is a thrust mode,
(and V/S the pitch mode with thrust whatever req. by the speed.
and thrust on your engine is what you don't want in a CDA
cheers.