What Anthill said;
It is extremely frustrating to try to apply, say, the fuel or duty time limit policy when you have to sit and explain to the other crew member what the policy actually means and allows.
Forget Aptitude, - what is needed is a 'Laziness and Arrogance Test' at interview stage..
When you have Co-pilots (and Captains who may have been in the small operation for a while) who once they are hired can't be bothered, and find that daily Flight and Duty program recording is too much, (among other requirements), saving the Company Operations money instead of scamming it for more than they think they can get away with, yet still expecting time off when they choose - would be a better test to reduce the interview numbers for a better overall operation in the long run..