I've never really worked on retrieving ,
well past the passing a toy on the house.
I find recall the key.
if they catch and your recall is spot on ,they dont want to leave what they've caught ,but the desire to come back ,will be enough.
Retrieving is a natural extension of recall. Get that 110% retrieving should be easy,unless they are retrieving shot game,or.blind retrieves ,but I don't need that.