Homebrew PCBs

hallo!

i'm making a lot of pcb's in big amounts and i want to built an 
etching tank. i wanted to know what is the best way to etch a lot of 
pcb's at once, and if there is a way to use less etchent for all the 
pcb's. i also want to know how do i heat the etchent every time 
without letting it touch heaters made of metal?

thanks a lot
mumin.