I made a lot of LED- signs . Drawing and milling the PCB´s took a long time. PCB are never even. Without using a vacum table the cutter gets to deep into the PCB. So i had to push down the PCB with my fingers all time long. Not very safe and boring. I had to find a better way!
Step 2: Working With a Paintmarker
A friend came up with the idea to paint the PCB by hand. With hand- I have a CNC machine! The next day I bougth some different paintmarkers and screw them to my CNC. It worked fine. With the black one there was a good line with no breaks.
I had to build a simple holder for the pen.
Step 3: Fish Tank Heater
I didn´t like to buy a ready acid bath, so I build my own. I glued some acrylic together. Bougth a fish tank air pump with tubes and bubble stones and two 100 Watt heater. The heaters make only 32 Celsius. I need 40 - 50 Celsius. I firmly opened them and removed the end stop. Then I put them up to 50 Celsius. All together less the 50.-€ (acrylic was free, from a friend). These heaters not made for what I use them. Do this on your on risk!