Painting and Finishing:
Your Beaver model can be left plain white foam or you can paint it with a foam safe paint. A couple of excellent paint options are as follows:
Model Master Acryl (brush or Airbrush).
Inexpensive craft paints
Testors Aerosol paints (be sure this is the newer
stock that specifically says foam safe on the label)
To help cover some of the dimples and the pebbled surface of the foam prior to painting use lightweight wall spackling compound to fill the small voids and dings (you can tell if its light weight just by picking up the bucket which will weigh almost nothing). You can then carefully sand with a 420- 600 grit sandpaper. Be careful sanding as it is easy to gouge the raw foam with a corner of your sandpaper. One method of reducing gouges is to cut a small circle of sand paper so there are no corners to dig in. To give a final really smooth finish mix some of your light weigh filler with water to a pea soup consistency and brush this on to fill smaller imperfections. This final coat can be left to dry and sanded or you can use a credit card to carefully squeegee off the excess while its still wet for a super smooth finish. A light coat of Poly acrylic wood finish will help your model resist scuffs.
For added durability and to resist "hangar rash" from handling and storing your plane you can also cover the model with lightweight fiberglass and Minwax (or other brands) Poly acrylic wood finish (be sure its Acrylic / water based!!!). A great article on glassing your models can be found here: http://www.smoothair.ca/content/view/83/43/
Glassing may sound like a lot of work but its easy and very satisfying when you have the finished smoother and stronger model.