Open the .fx file in notepad.
Then scroll until you see things like
float BrownSepia
<
string UIWidget = "slider";
float UIMin = 0;
float UIMax = 1.0;
float UIStep = 0.1;
string UIName = "filmgrain amount";
> = 0.0; or
float Color
<
string UIWidget = "slider";
float UIMin = 0;
float UIMax = 1.0;
float UIStep = 0.1;
string UIName = "filmgrain amount";
> = 1.0;.
You see what they do if you read it

You have to take the lowest line (like > = 1.0) and change the amount by changing the number.
Sry for the bad description my english is bad but I hope it helps you