Getting post effect shader

[Rick]

If I have a post effect shader assigned in my scene on Root, how do I get that so that I can manipulate it's value with SetFloat("var", value)?

[shadmar]

local shader=Shader:Load("some pp shader") to get a handle.

then send the float using shader:SetFloat()

[Rick]

I was confused because normally Load() doesn't get a handle to an existing thing but loads a new one but shaders must work differently.