I would have to say with short game training, I’m very big on controlling trajectory and distance with wedges. I like to see my students hitting through different windows while still controlling the distance. For this I have different height ropes hung at the driving range that I use.
With putting I would have to say my favorite aid would be a putting mirror with lines. This allows your eyes to be right over the golf ball while also allowing you to control/see the movement of the putter face.