I've made a huge rhino before. You would probably go about it the same way. You'll need a model to go off of. The should be wadded up paper in the general shape for each part. You'll need a lot of tape, too. Paper mache over each part to get the exact shape you need and to make it smooth. You might have to paper mache over wired for support in heavier parts. You can use hangers. After you have the parts (tire, seat, handlebars, etc.) put it all together and put another coat on it to smooth the pieces' seams out.
