How to apply shaders to specific layers

I'd like to apply a wavy shader to a background layer like the giygas fight in earthbound but am stumped on how. Is there a way to isolate shaders to layers or even just actors?

Check this out: http://community.stencyl.com/index.php/topic,57431.msg303085.html#msg303085

That's cool but I'm kinda lost as to how this was really done. Also I've read that there was supposed to be new blocks for shaders like adding them to actors and layers. Kinda curious as to when that's happening.

The Image/Actor shaders work on images and actors (like the title says   )
So you could create a large actor and apply such effect on it. But you would need to investigate and trial and error with the shader code. And be aware : shader code is not easy!

(background) layers might be effected by the scene shaders.
http://www.stencyl.com/blocks/viewCategory/scene-shaders/shader-apply