This is the photosensitive pcb I am using: https://www.bungard.de/en/consumables/consumables/presensitized-boards
The time in the natrium hydroxide is about 2 min. Its easy to see when its finished, because the design will get visible as light purple traces. I wipe very light with a soft brush until I see no more changes.
The ferro 3 oxide needs to be warm, 40 degrees C or more, to etch it very fast and clear.
This is my pcb of the twin t drummer:
Normally I etch pcbs for smd, the small pads and traces are no problem.