The name 'stamping', is likely why you are having trouble finding information. 'Mask' would be a more accurate term, since you want to cover/protect certain areas from the chemicals.
Need to be a little more clear. How many of these PCBs are you going to make?
If this is just a single board, and not too complex, you can use a permenant marker (Sharpie brand or similar). Sometimes you can use tape if the adhesive isn't weakened by heat or water (common black electrical tape works). There are rub-on decals (Press-n-Peel).
Since you have a machine that washes the PCB with the etchant, I'd guess you will be doing a lot of boards, or you are a student and your 'supervisor' is your instructor.
Give more information, if this is for a business, and you plan on doing a lot of PCB, we can give a better suggestion to meet your needs.