"I was told that they were flown by volunteer Greek Air Force pilots."
If that is true, then possibly that is part of the problem.
Firefighting is a very specialized and dangerous type of aviation. With all due respects, what skills and experience long term, would a serving military pilot have to go firefighting? The job is dangerous enough for current and experienced personal.
They should contract in serving firefighting pilots, if they are available, or failing that experienced and current Ag pilots. No only from a safety point of view but for getting the job done effectively.