So you've applied your clay, and a you're staring at a blob. Firstly you need to create your rough shape. The best way to do this by using a tool with teeth such as a Surform/Rasp or a Rake. Rakes can have smooth or serated edges- which help to cut through the peaks and troughs of the clay surface. It is possible to cut teeth into one edge of a smooth rake using a bandsaw to provide a dual purpose tool.
Once you have a final form with all the details carved in- you will need to develop the clay surface for painting or to take molds from. There are several stages in developing the surface, each of which improve upon the last stage, almost like grades of sandpaper.
Finishers are similar to rakes with smooth edges. Used in a criss-cross motion across the clay surface, they smooth the imperfections left behind by the rakes.
Steels are the last tool to actually cut the clay. Quite simply, a steel is a sheet of Spring Steel which is available in many different gauges down to small fractions of a millimeter. Work your way down through the gauges until it is hardly removing any clay. Steels can be found in many shapes and sizes or you can make your own from a sheet of Shim stock steel to suit your job. Basic shim stock is available from good tool supply companies. In the US, McMaster-Carrs shim stock assortment- Part Number 9300K27 - .003 Feeler Gauge stock 2093A16 is recommended. You can download steel templates from Chavant
Slicks are the final tool to bring out the surface of the clay. Slicks are made from sheet Lexian (plastic) with polished edges to burnish the surface of the clay. Again they are available in many shapes and sizes to suit your model. It is possible, using slicks, to get a surface that you can see your face in.
You can read articles on surfacing on Chavants website in the technical articles section.
For the professional studio, it may be worth the investment in a CNC Mill such as those produced by TARUS. http://www.kolb-technology.com This can speed up the modelling process massively using 3d Modelling applications such as Rhinoceros. CNC machining is a subject all on its own, for further information on this subject contact TARUS, MORA or AAD
To help with the problem of Symmetry on your model, The Symetra Modelling Platform is available. Designed by Dan Scigalski, the Symetra is a precision machined armature and measuring bridge. For more information see email Dan or firstname.lastname@example.org