Good starting primer on injector servicing:
HOW-TO: Rebuild Diesel IDI Injectors
Setting/balancing the pop pressure is tedious, messy, and time-consuming. Test, keep good notes on pressure readings, verify no drippage when pressure held to just under pop for several seconds, disassemble, reshim, reassemble, test again...
Not to mention cleanroom conditions.
Not to mention inherent dangers involved in high-pressure fuel jets near the human body...
Next time I need to service the injectors, I would probably find out from v8volvo who these "Local guys here do it for a few bucks an injector" are!