Easiest way to do decals is with transfer decal paper than can be bought for a few sheets pretty cheap on eBay here in Oz.
Used the stuff on my 4 builds with an ink jet printer and created the logos in MS Paint from memory. Not a huge selection of fonts but good enough and was way too paranoid about importing viruses by downloading fonts from the net.
If I was to do them again I would set them out so that the section to be cut would fit the size of the headstock and then no edge lines are visible. If you want a black headstock face just do the logo or lettering reversed out in a solid black background. Saves heaps of mucking around masking up and painting. In fact one idea I have in mind is to take a photograph of something and reverse that out so that it almost has a 3D look, or maybe have that 'something' placed on a black background. Same can be done if you want to achieve a clear headstock by placing the object on a white background however if there is not enough White colour balance it may add a slight opaque hue.