>What is needed to make 4 layer boards, a press (hot or not) and some sort of >glue? > >JT
I sucessfully did this with 5 minute epoxy and a homebrew little simple press consisting of two vices.
The most important part though is that you definately will need a through plating station or else you will not be able to connect the inner layers to the outer ones - errr, or then you have a method I'm sure others would be interested to hear about.