Description: EfaPlast is a clay-like sculpting medium.  It is "air-drying" and no baking is necessary.  I suspect it's a blend of ultra-fine paper fibers or ash and glue, like the "paper clay" products.

Review: EfaPlast has a delightful silky texture that makes it easy to work with straight out of the package.  It's not as sticky as epoxy or polymer clay.  In fact, it doesn't stick very well to plastic.  For a secure bond, you will need to glue the parts to the pony after they dry.
Working time is anywhere from 1 hour to several hours.  By spritzing some water and kneading it in, working time can be extended.
Texture is very fine, so subtle details can be achieved.  However, it is very soft and it doesn't hold it's shape very well.  Sculpted parts may sag with gravity.  It is good for work with flexible molds.
After it dries, this medium shrinks slightly.  It is VERY light, which is nice for larger projects.  The texture is matte and slightly porous, like a sheet of paper.  You can smooth wet clay over the dried parts to get a smoother finish.  However, finished projects are not as durable as polymer or epoxy clays.  I could easily snap a piece shaped like a 1/4" thick coin with my hands.  Consider coating it with a clear glaze to increase durability.  I don't think it's water-proof either.
Cleanup is super easy!  Just water and a little soap will get you squeaky clean.  Also, this material is non-toxic, which is nice if your kids are customizing.

Please see the Sculpting FAQ for a comparison with epoxy and polymer clays.

Efa Plast Light made by Eberhard Faber

The gargoyle pony on the left has wings, horns, and hooves sculpted with EfaPlast Light.

Description: These rub-on transfers are attached to a plastic-like sheet.  They also come with a popsicle stick, so you can apply pressure and transfer the design to your item.

Review: These rub-on transfers are very easy and quick to use.  However, they are hard to apply onto curved areas, like hooves.  The design cracked a little during the transfer.

You can cut the design into pieces and even layer them on top of each other.  I will be covering the designs in matte varnish and will add an update addressing durability later.

Also...coming soon: review of Elmer's Painters opaque paint markers.  So far, they're not bad, but designs can peel off when the pony is handled!