What's the right way to run a second pass shader in XNA?
In XNA 4.0 what's the right way to set up a "second pass" shader where I want to take a frame that's been rendered and then run the entire rendered screen through a shader program?  

Is it possible to run a third pass as well?

What's the right way to run a second pass shader in XNA?
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In XNA 4.0 what's the right way to set up a "second pass" shader where I want to take a frame that's been rendered and then run the entire rendered screen through a shader program?  

Is it possible to run a third pass as well?
