Installing injectors

or just disconnect the return line and loosen the supply line. the head will drain after that. and you wont blow any debri into the fuel galley.

 

I have never heard of a licensed mechanic. Certified yes. What little dab of fuel in the cylinders getting in the oil isn't the concern, the concern is that much fuel being compressed when you hit the start button. Usually breaks a piston between top and second ring. That's when you get blowby and oil consumption after an injector swap. Not the all famous line of the bad injector washed down a hole. Like Superhauler said pull the lines into the head you will have less trouble.