[SOLVED] Apply filters (Blur) only to an object/material

I just saw this excellent tutorial to reduce the noise:

and my brain has been exhausted and burned. I definitely not yet able to understand that.

So what I need is to apply Blur only to an object or material (on a scene with many different objects).
In Cycles, Is there a simple way to apply filters by objects or materials?. Or better the question related to what I saw in that video:
Is it possible to choose as “Determinator” an object or material in the Bilateral Blur node?

Without knowing much about it, I guess the problem is that it is not possible to determine exactly what will be the edges/limits of each object in the resulting image of the render. But ask this in case someone knows a easier way to do this that I want.

I just found this about “Render Layers”:

I guess this solves my problem about to be able to apply filters only to an object of the whole scene, right?

You would need to isolate the object you want to blur. Either put it on its own render layer or create a mask to mask off everything else in the scene. You can add a Pass Index number to any object or material, add enable the material or object pass to the list of render passes. Then you can use an ID Mask composite node to create the mask from that render pass which you can then use in the composite to apply effects

Thanks Richard.
This is another tutorial that helped me (for things related to the masks):

I see that the hardest part is to get a good separation of the edges/limits of the objects.
I have used as “Determinator” the object Index with anti-aliasing in ID Mask node. Also the highest value of Color Sigma in Bilateral Blur node.

Since this is a process that seems repetitive and automatic, I wonder if applying filters by objects/materials could become in an object property for postprocessing. Adding a basic option that does not require manipulation of nodes.
I do not know, maybe that already exists and I do not know how.