Anyway, I know what the problem is that you are having. I've found the same problem. No matter what speed and power you engrave at on your Epilog, it will always look better on the second pass. The issue is that the sprays that you are using leave a residue on the copper that your laser just burns on. For example, when you use the black and do two passes at 600 dpi, full speed and full power, it looks like it's all gone. Try a red or yellow spray and you'll see a fine residue of pigment that stays on the board.

I haven't worked out what spray will work yet. Clears and acylics/enamels don't seem to work. Or wax. Last thing that I was trying was white-out (correction fluid). The way that you are doing it will give enormous etch times with poor quality.

Hope you can work it out.

The RepRap team introduced a simple breakout shield -

The Arduino Breakout Shield is a shield that plugs into an Arduino and provides all the Arduino pins as screw terminals. It is perfect for semi-permanent Arduino projects, or just general prototyping. It provides access to all the Arduino pins, as well as providing extra GND, 3.3v, 5v, and Supply voltage pins for convenience.