This instruction is about how to apply solder mask to PCBs. It is assumes you already have traces on a PCB (regardless of etched or milled) but no holes yet, like figure 1. You also need artwork (black printout to transparent foil) containing only pads (EAGLE layer 17) and vias (layer 18). Make sure it is really dark. We also suggest filling out the holes (you can use a black marker, e.g. this one or that one). The room you are working in has to been protected from of UV lights, e.g. use 05 EG 027. It has special lamps and no windows (avoiding sunlight).
Set up lab (figure 2). Other resorces are mentioned in the text.