I have become quite good at Banana flick. I use it all the time now. My main problem is not executing it, but rather to be able to read the service properly because if i try to execute Banana flick on a half long or long serve thats a high risk to make a mistake !!!!
Yet, my technique is not perfect because so far if i have fairly good % of execution, I have not much variation in execution.
1) it is important to know on which serves it is easy to make the banana flick. Because of the side spin, some serves are easier to receive with the banana flick, some are more difficult, and a normal flick (or push) is to be preferred... but usually reading the serve is the crucial point
2) timing wise, always hit the ball just AFTER the top of the bounce. Banana flick on short balls, always step in, keep your upper body low (as well as your lower body) and move your free arm towards the ball to have a good balance. the free arm is really important.
3) assuming you are right handed and receiving pendulum serve from right hand player:
always go for the diagonal. if the serve goes in the middle or 2/3-3/4 BH hit the ball slightly on the side and aim for the opponents BH. i would another usually play BH behind it or sometimes pivot directly.
if the serve goes to the FH, hit the ball sideways on the back (= gesture parallel to the back line) and aim on the deep FH of the opponent. it will surprise a lot of them. However if they get used to it, they will attack strongly with their FH so get prepared to make a block with your BH covering the middle as well into the opponents BH. if it goes to my FH, i improvise. i am rather good in FH.
if the ball goes too much on the BH side of the table, execution is too difficult, i prefer to go for a push or stop receive with the BH.
4) if trying to receive a BH serve on the FH from rightie or a pendulum serve from a leftie on your middle on FH side, then aim middle or straight. put less speed more spin because there is less table. in doubles against FH serve its a good receive as well.
5) against YG serve (= reverse pendulum serve) from right hand player in the BH side, don't do the banana flick, do the normal flick, with a more forward move, and arming the wrist at 6 o'clock. surely its not impossible to do a banana flick, but i think its much more difficult (as for me, i cannot do it consistently against this serve)
6) Lastly, remember that for a banana flick, when arming, you should twist your wrist and the tip of your racket should be at 3'clock . if not, you're just doing a flick, not a banana flick.
7) Usually i need to decide BEFORE the server serves that im going for banana flick if he serves short. but the serve is short, but sometimes i feel its got a lot of underspin, then i decide at the last moment to stop-receive short. the execution of course may well be approximative because its a last second decision, however, the opponent may be surprised as well...do not commit for this banana flick if the incoming ball is too difficult