When painting an MDF piece of terrain, what do you prime it with? Any other tips for painting?
My best results have come from rustoleum filler primer.
Two coats and that's it. Since mdf soaks up paint like a sponge, you need a good barrier or else you'll be there all day. Other primers work ok too. I've gotten auto primer from dollar store that worked just fine, for example.
Cardboard is actually pretty bad ass, if you fill them from below with non-expanding foam (like window/door seal foam) to make them more hardy.
So I looked at those cardboard building, and considering grabbing a pack since they're so cheap. Are you filling the entire building with foam, or just reinforcing the corners? Seems like it would require a bunch of foam to fill the entire building?
There's a few ways. The hard way is to cut EPS (pink stuff) foam to size and insert.
The easy way is to just squirt the can into the back (building laid top down) and then when it dries if there's any excess that spooged out the top, use a bread knife or hot wire cutter to trim.
One can of the foam can do maybe 15-20 4x4 buildings if you use expanding foam, but be sure to use some scrap wood and clamps (or screws) as a form so the building doesn't bulge. Non/expanding foam is better but one can will only do 3-4 medium buildings as it's basically 1:1 filling from the can.
Alternatively, if you spray the interior of the cardstock well with a water barrier (clearcoat or something) you can use cheap-as-shit plaster of Paris. I initially made the mistake of trying this and not coating it and the ink bled out like a stuck pig, and they warped like a MF.
You can also use other barriers like wax paper with the seams taped with painter tape, or if the buildings are uniform you can make a mold.
I gave all my papercraft shit away because I like modeling, but there's a ton of free/ cheap shit out there if you have a decent printer (I had a color laser at the time) and don't mind using a razor knife.
The alternative to all of this is just using EPS to make buildings by cutting the same sized rectangles and stacking them to height. Just PVA glue them together. Trim with bread knife or hot wire and you can use plaster or hydraulic cement to creste a cool faux stucco effect. Then just spray paint with Rustoleum sanded paint for a middle eastern look. 40$ will make you an entire tables worth. If you want to get fancy you can buy foam spheres (green) at Michaels, cut in half, and glue to the top for a legit dome on the top like I see with ME style terrain all the time.
Cheap shit and awesome because the EPS scraps can be made into anything you can imagine - trees (trunks), mountains, rocks, whatever.
I grabbed Zinnser B-I-N shellac to seal/prime after reading up on various methods. It runs through an airbrush without needing a thinner and can even be used to dip smaller pieces without clogging detail.