Playing X-Wing sort of got me back into miniatures painting (mostly touch-up work), which got me looking up scratch-building and model making sites, which led me to a blog titled Solipsist Gaming run by someone who creates a lot of simple models and homebrew rules as a hobby. I was particularly intrigued by how he made starships by manually hollowing out shapes in clay and pouring in resin or plaster of Paris. (Well, that and gluing pasta together, but one thing at a time.)
I already had spare paint, and I did some resin casting back in my Warhammer 40,000 days. I have a lot of old Sculpey, but it's a little too stiff to take deep impressions even when it's fresh. Plasticine works well, though, and it's three bucks for a pound. The casting compound I used is even less.
Step 1 was sculpting a vanilla hull shape out of spare Sculpey and baking it. I pressed that into the softer clay to give me a starting impression, then ad-libbed the surface details with various tool tips and paintbrush handle ends. Next, pour in the plaster and wait. Pop out the dried shape, sand off the excess, then paint on a quick base coat followed by a thin black wash to darken the crevices and some soft edge highlighting. Then I drilled a small hole in the bottom and stuck it on a spare X-Wing ship stand. The whole process was pretty informal and experimental (i.e. sloppy) just to feel the process out.