Homebrew PCBs

I know there are many ways to make PCB's, but I am trying to figure 
out how to make a auto etcher. The building part is easy. The 
problem is where do you get the software and how does it work? 
Currently im using old 5 gallon fish tank heater and air stone to 
etch boards and is very time comsuming when make larger boards. 
Thanks in advance for your time and advice.