I'm pretty sure Rasterize will have a better recommendation, but so far I've been doing mine by using the CAD program to export DXF of the important shapes, then transmute the DXF to SVG using an online converter or
dxf-svg-convert
Once I've got an SVG file I use
Inkscape to color things in. Lots of tutorials for Inkscape on youtube. I've been doing a play-by-play on the
FW-42 Mini skin in the past week or so too. Nothing as nice as Stephen puts out from an artistic perspective, but it's nicer than white foam