A properly trained Mashgiach is required to have good eyesight ($20 bill test), patience, serious, yiras-shu'mayim", etc. Of course he is to be compensated more that a regular mashgiach.
In each area there is to trained qualified infestation mashgichim that will go around to the various establishments "just checking their leafy vegetables & herbs", as coordinated by the Kosher certifier.
The regular in-house mashgiach will be trained just for leaf miners and pearled barley, etc.
In an area that has currently 50-75 plus mashgichim for food service, 5-10 trained mashgichim for infestation should be trained.
BTW- In Eretz Yisroel they have roaming mashgichim for "nikur", Terumos-maasrois, infestation, etc.