Thanks for this guide. I used it on my HP3525. I added one step which was to put a few millimeters of distilled water in a small dish and stood the printheads in the water for a few minutes then I gently lifted and lowered the printheads. The amount of black ink that came off was amazing. My first print was almost perfect.

I agree that removing the PCB screws is not necessary and risks damaging the connection between the PCB and the Head.

Hold the top lid so it doesn't crash down behind the printer