FCOM 3.03.20 details visual approaches and has a couple of nice diagrams to supplement these along with the associated timings. It is not clear from your posting how your TRTO is teaching you to fly these. In our operation we follow the airbus FCOM procedures and FCTM and fly as per the diagrams and they work out nicely.
The "donut" is just another aid to assist you in the approach. Supplement this with the papis/vasis/dme/prog page distance to RWY/mach 1 eyeball etc to get yourself in the slot.