As stated already, it is considered professional to make your initial brake application hard and gradually release it as the train slows to a stop, rather than constantly applying and releasing in quick succession - known as "fanning" the brake.
This is what I've been taught is a "perfect" stop using the Westcode brake.
1) initial application is step 2. Keeping step 3 as a reserve incase of misjudgment or poor braking performance.
2) on approach to the station, usually around the vicinity of the platform ramp, release to step 1. Keeping step 2 and step 3 as reserves to adjust the position of the train in relation to the stopping point. As previously mentioned it's an hole-in-one if you can stop on just one step without having to reapply the brake.
3) select Off and Release when the speed drops to 2-3mph, in the time it takes for the brakes to electrically and mechanically bleed off the train should stop naturally without any noticeable jolt or shudder.
4) return to Step 1 to hold the train.
Even on notchless braking systems, like the 67s which have the PBL system that is fully variable between 5 bar (release) and 3.35 bar (full service), I've been taught it's still a good driving technique to have fixed pressures as found on a notched train, example; 10% = HOLD, 30% = STEP 1, 60% = STEP 2, 90% = STEP 3, 100% = EMERGENCY.
A factor I know that affects braking performance is blended brakes - in many cases the brake force supplied between the rheo brake and the air brake is not in sync. If a train is slowing on an adequate brake force supplied by the rheo brake but the brake force provided by the air brake is weaker than that previous supplied by the rheo brake then more air brake pressure is required to compensate for the lost brake force during the transition. Example: a step 3 application of the air brake may be required to achieve the same amount of brake force provided by that in step 2 when the rheo was activated. It can also vary vice-versa by also having crap rheo brakes but powerful air brakes.
To O L Leigh, I know 315s have rheo brakes but I don't know if BR/fGE/NXEA/Ganglia has ever disabled it? Do 317s also have rheo brakes? I believe they don't.