Same here, I seem to have got the hang of it. The thing I find annoying (at Marylebone anyway) is there is only the tiny dot matrix text saying "EXIT" - the green light doesn't light up like it would for my contactless card. So when following someone through the barrier I end up hesistating for a moment to make sure it is going to let me out! A more obvious visual or audio acceptance indicator would be useful
I always wait until the gate is closed before tapping my card on the barrier.
The design of standalone readers in the Light Rail system in Hong Kong, and also the First Class validators on East Rail Line, is that there are 3 lights, red, yellow and green, under the dot matrix display which can be unclear over time, with audible sound as well. If a card is rejected red light is shown, while if it is accepted green light is shown, unless when it is run out of value which yellow light is shown. Simultaneous yellow and green lights are shown when auto top-up is activated upon entry. There are also different sound for a rejected card, an accepted card without discount and an accepted card with discount.
There are no such lights indicating acceptance for the gateline readers in the Hong Kong MTR system, instead, a light indicating discount cards is installed which ticket inspectors can see clearly, also with different sound as well.