I spray painted my last build and it turned out pretty good. I used no poly or sealant beforehand. Keep the can far away from any exposed foam (spray at a distance). If you get to close the propellants will eat the foam. And of course since your basically spray painting paper use very light coats.
One issue I had was fibers in the paper standing up which I probably could have gotten rid of by lightly sanding between coats but I didn't care.
The hardest part was remeremembering to stick the masking tape to my shirt before applying so it didn't tear the paper. (thanks Peter for the tip). Be careful when masking any tape that you have painted.. The spray paint I was using did not bond to the extreme packing tape very well.
You can go a lot of directions from just simply spray painting with almost any old enamel in lite coats as described above to creating a really slick finish by investing a little extra time. The simple spray paint job isn't bad. It usually looks pretty good and you just don't have any time invested in it. If you don't think the airplane is going to have a very long life span then this is probably the way to go.
My slickest paint job ever on DTFB was created by Minwaxing the whole airplane and letting it dry 24 hours. I followed it with lite coats of Krylon (I think) after about the second coat I started sanding the whole airplane between coats with 320 grit sand paper and ultimately 600 grit before the final coat. The finish was amazing in the end. It looked like the whole airplane was expertly covered in Monokote! It really didn't require a lot of work, just patients in sanding and waiting for the paint to completely dry between coats. Hope this helps?
Mike
I don't think it adds any at all. Just wipe it on and then wipe all of it off that you can. I've found the poster board sections. (IE turtledecks) usually need an extra treatment of Minwax. The paper seems to try to soak up the paint and that causes some splotches.
Have you ever used painter's tape when taping over coats? I wonder if it would come off more easily, but still hold a good enough seal.
Blue painters tape is exactly what I was using. Like I said the paint just didn't bond very well to some extreme packing tape that was reinforcing the nose of the plane. I never noticed any paint being pulled off the foamboard itself.
My slickest paint job ever on DTFB was created by Minwaxing the whole airplane and letting it dry 24 hours.
Oil based Polyurethane is what FT recommends.
I used the oil-based Minwax without any issues. I saturated the paper with a 2" foam brush, then wiped off the excess with a paper towel. The only thing I noticed was that it softened up the hot glue. Once it cured, everything was fine. I didn't experience any foam damage or warping. Anyone airbrushing their planes? That's the route I'm taking.
I use water-based acrylics in my airbrush. I plan to try some automotive, gravity fed spray guns, but I have not had a chance yet.
This is the set I plan to try: http://www.harborfreight.com/air-tools/paint/professional-automotive-hvlp-spray-gun-kit-94572.html
The spray guns I have are very similar to those. I think I'll give the acrylic a go, cheers.