Suggestions for a suitable Modeling medium?

If you are used to working with wood, why not try Balsa wood, you can buy it in sheets from model making shops which you can then glue together (i use impact adhesive but i guess PVA would do the job too). This would give you the layers you need, and aswell as being workable with sandpaper etc it is also soft enough to cut with a small hacksaw or even a scalpel blade. An advantage would be you could also use the same woodstains and paints as you would use on ply, so it should give you a good interpretation of the finished products. :-)