practise, practise, practise.. Yes, it is hard.. It's good for the brain, co-ordination.. A very long time ago, when I was having trouble playing something. I just stopped and 'talked' to my brain for a few minutes, telling it, I would be patient. But we were NOT going to quit until I got it right.. Repeating the procedure of playing the song, lets 'muscle memory' kick in.. That is, your fingers start to remember where to go, without your brain having to re-calculate, and send control data to your hands.
I was watching the little boy (from India I believe) who won the national spelling bee. He would spell out these incredibly complex words by 'fake writing' them on his wrist as he went along.. He was using muscle memory to spell.
Honestly I usually don't play my Genos in 'real time'.. I record into Logic Pro.. I might be able to play the song, but just can't keep track of all the button pushing in between. My hat goes off to you folks, who do it in real time..
Certainly playing an arranger kbd, is a totally different beast than playing a piano..