Have a look at this youtube video I found for a demonstration of how to apply a pinwash http://www.youtube.com/watch?v=63j_cX9ZK60
Also note that he used a different paint type for the wash then what he used for the main paint job. This means what thins the wasn/pinwash has no effect on the base coat below it.
As for Future, think of it as a gloss Clear Coat.
It does three things:
-Protects paint layers below it with a clear durable layer.
-Creates a smooth surface allowing for proper application of decals and will let highly thinned paint to flow by capillary action along seams and such. The last being very useful for highlighting panel lines.
-Creates a gloss coat for when you want the finish shiny. If you don't want it to be shiny you can mix it with a tamiya dull coat [I forget which one] or just paint it over with a dull coat.
As for shading, there is pre-shading and post-shading. Pre shading goes on before your final paint job and darkens the surface below and post shading goes ontop of your finished paint job and places dark colors ontop of your finished paint job.
I hope this helps with deciding how and when to use Future.
Mongol General: Conan, What is best in life?
Conan: To crush your enemies, see them driven befor you, and hear the lamentations of the woman!