@foone iirc one of the tricks was to add some sort of clear oil (like baby oil) to stick it to the PCB, which made the white paper go kinda clear.
the actual home etching process is super messy though. ferric chloride stains eeeeeverything, it's bad for your skin, and you have to neutralise it before disposal which also creates a lot of mess. I used to own a kit and used it only a couple of times because the cleanup is horrible.