ANIMATING PAINT EFFECTS

I am trying to animate a brush along a path.

First I select the nurbs curve, then I go to Visor and select my brush.

Rendering Menu - Curve Utilities - Attach Brush to Curves.

Then I select the brush curve - attribute editor - end bounds - and change the values of Max Clip.

Everything seems to work out fine and the brush moves along the path as I move Max Clip.

But when I try to set keys to animate it and hit play, nothing happens.

I am not sure if i understood your problem.But if its that i understood these settings are not taking any keys by default.Try to render a small scene and you ll see that its animated.

Right click on the Max clip and hit "set key" in the desired frame....
You can also preview the animation curves in the graph editor

try the flow animatin thats in attribute of paint effect.