Hi there,
As an engineer with over 15 years of modeling, prototyping and effective manufacturing of different kinds of products (ranging from wellbeing/personal care, to alternative energy), I could make your model within 4days at high quality of detailing.
Unfortunately I don't use to draw on paper anylonger, but if it's a must, I'll return to paper and colors.
Anyway I prefer to work directly on CAD program(Autodesk Inventor), because is easier for collaboration - I make a draft for your product, you make notes on it, I modify and send back, and so on...
What I'll deliver to you: 3D model in different CAD formats (iges, stl - for 3D printing, step, obj - for embeding in webpage), 3D pdf - so you'll be able to open and manipulete with the regular Acrobat Reader, drawings and renderings.