Model Railroad Magazine (If its still in print) was the standard Rag for most Modellers since the 50's IIRC.
3D Printed N scale locomotives huh? What price per Cubic Inch are you getting? What kind of Material? Do you know what kind of Printer its being done on (Make/Model/Type, this can greatly affect the method which is used to print it)? Presumably you're just getting the Shell printed? Or Trucks too?
If you're going to be serious about painting Models, you REALLY want to go buy a cheap Air brush. used to be you could by pumps for as little as $100. Pawn Shops are a great place to go looking for deals as well. You can do the Aerosol Can route, but thats a pain and works out more expensive in the end unless you're just painting a couple models.
You can do Brush Painting, but be ready to go looking for practice models to experiment on. Don't sit down with your most recent most expensive acquisition with ideas of perfection, because it ain't gonna happen. Picking up a few $1-$5 Gondolas at a train show is a great way to start because Gondolas have always been the most ugly things on rails no matter where you go anyway.
Falcus
3D printers have come way down in price with the quality going up and up. There are two different kinds that are useful for us. The first is a fusion deposit type, which is basically a hot-glue gun nozzle mounted on a printer. Each dot is squirted out and while the plastic is still hot a squeegee burnishes the surface before the next layer is placed down. The other kind is stereo lithographic or SL-printing which uses a laser and a photo-reactive liquid plastic. This system will produce higher-resolution objects with fewer artifacts, meaning bumps and lumps than the FD kind. There are advantages and disadvantages between both kinds and it depends upon their use. There are many factors that need to be considered when 3d printing including the cost per object, which is based on material use and output time. Sometimes it's not worth the cost of the materials since there is no ROI on producing the part. Also keep in mind the output time. A simple object can take 2-3 hours or longer, depending upon the size and complexity. Hollow objects, depending upon the printing method, may require reinforcement inside, while some objects require supports to keep them from collapsing. The other thing too is to produce the part, you still need some 3d modeling experience, or even CAD and drafting experience in order to understand intersecting geometry, complex modeling, and other things, otherwise, there is nothing but wasted material. Granted, things are a lot easier than many years ago, but still you need this knowledge.
When done properly, these parts can be highly accurate. My brother repaired the hinge and latch which got broken on my computer case. He measured the parts using calipers, recreated it in his 3d modeling program (I can't remember what he used), then output them, which took about an hour for the tiny parts. in the end the parts fit perfectly after he cleaned them up by removing some little bits from the supports. There were no other part modifications needed, and other than being grey instead of black, work just like the originals.
These printers range in price from under $1,000 for the low resolution FD kits to the $100,000-plus range. My brother just picked up a SL-based printer from Form Labs. This is a $3500 unit that is made in this country, and only 30 miles from where we live. He uses it for prototype modeling and for masters for his spin-casting business. He produces a 3d master, that is imprinted into un-vulcanized rubber under pressure. Once the rubber is cured, the part is removed and then he uses this to produce pewter coins, medallions, and other things for customers. His Form Labs printer uses an ultraviolet laser and the stuff can be cleaned up with Isopropyl alcohol. If there is any gluing to be done, since there is a limit to the size of the parts produced, he uses a cheap, like $22 green laser pointer he got on Amazon along with a dab of the liquid, uncured photo-reactive plastic.
John