Now the trick for etching brass is that the etching must be the fastest possible.
That means that the bath musn't be clogged, the Perchlorure de fer (okay, can't remind how to say that in English), it must also be stirred and heated
So in an old aquarium I put 2 liters of the acid, an aquarium heater and air pump and dipped the fret in it.
You can see pretty fast if things go well. look below the parts pop out of the metal
Then when the parts begin to fall apart, better clean everything and get the parts
Let's filter the water, dry the parts and clean them with Acetone so that every trace of the photoresist material can be wiped away.. and time to start the building of the diorama