Texturing, sculpting and compositing

Hello everyone.
I'd like to know if it's possible to directly paint on meshes and if there's support for sculpting.
Last, not very relevant, is it possible to do compositing (post processing) on renders?

Thanks in advance for replies.

Ok, realized I can paint on meshes.
I also guess sculpting is done with stitching curves (isn't it?)

Please, give me advice on compositing (applying filters and post processing to render).

Seamless3d III is a nurbs patch oriented modeller. In most of my modelling tutorials the patches are automatically stitched together but you can manually stitch them too:
http://www.seamless3d.com/stitching-nurbs-patches/index.html
In making Seamless3d III easy for nurbs modelling, many of the older functions related to direct mesh editing were broken but when I can find the time I will restore them back to working order and make some improvements, taking advantage of some of the ideas that have come about from nurbs modelling that are relevant.
I am not familiar with compositing, I would need to find out more about what it is.
When making animated movies I use PovRay to render the scenes. PovRay is a free open source ray tracer, great for adding shadows.

At the most basic level, it's all about allowing one or more shaders for each rendered object.