Hi,
If you are building a static model almost any material that can support its own weight will do, balsa each side of a hardwood central spar should be easy to sand and then paint.
For a flying rotor blade even a model, your oprions are again wood, wood covered in composite material, hollow/foam/honeycomb filled composite.
Trying to carve/sand a blade from solid carbon fibre pultrusion is NOT the way to go.
In any rotor blade it helps if the centre of rotation, the centre of gravity and the centre of lift are as close as possible, frequently at about 25% chord.
In order to achieve this it requires a nose heavy construction and very light tail section, hence the requirement for at least parts of the blede to be hollow/ foam/ honeycomb filled.
The other problem with using most pultrusions is that all the fibres are running along the pultrusion and as such the section has very little torsional rigidity as well as being prone to splitting.
If you are really serious about building flying blades, email me at sms@performance-composite.com
Before I set up Performance Composites Ltd. I was an engineer at Westland Helicopters, developing composite rotor blades since 1975