Here's a quick overview of the Denoiser settings by Jugaad Animation.
This is an image tutorial on Denoiser, the new feature added in Blender 2.79.
If you want to denoise in compositor, use this [node setup.](https://i.imgur.com/jx85J50.png)
To get even more control, you can enable render passes and individually blur them using the node setup. The render passes then can be added using a color mix node.
I would love to make short tutorials like this. Do let me know if you have any request.