Just had a look at that blog. It's pretty good basic advice for those looking to get on the ladder (FWIW I was in Ab Initio 1 !!! and am now happily retired) Realise the job is constantly evolving. Nothing is set in stone. It is difficult to quantify exactly what we are looking for and some people make it into advanced stages of training before we, or they, realise this is not for them.
Personality plays a big part in the selection. You have to be a team player, yet capable of functioning on your own; of making decisions and abiding by them, but always having a plan B and knowing when things have gone rat!!!! and it's time to implement that.
Getting though the selection process is not something you can learn - nor should you want to. It won't help you at all should you be selected. It's not 100% a scientific selection, a lot is based on gut feeling on the part of the board, but if you get to IANS you have just become part of a very select group; those who make it through the training process and validate at MUAC have joined the ranks of the best controllers in the world