Rating staff

I can understand how researchers can rate players, all you need to do is watch them in matches a few times. However how exactly do you rate non playing staff? While you might be able to rate Mourinho's man management or Wenger's working with youngsters to an extent, who decides Bristol City's GK coach's level of discipline, Port Vales physio's physiotherapy rating or the judging current ability of Wrexham's youth coach? I guess a lot of these stats are randomized for lower league staff but still how would you be able to rate behind the scenes staff at any level unless you know a lot of people within the game? Does Ray Houghton or somebody like that do this for SI?

iirc all the club's researchers rate staff as well as players, and they can be quite well connected with the clubs

Yeah, the researchers do it.

I think the Port Vale researcher would have no trouble rating his team's physio, for example. A GK coach's level of disciple would be harder to be and probably randomised.

Would the researchers watch the staff in training for several weeks to find this out? And what would they have to compare it against, they'd have to be familiar with staff at other clubs wouldn't they?