Hello AdamAnt
Put the top parent node of the scene tree to a render layer. That will give you a) the entire render with a transparent background (so you can toggle off alpha in render settings) and b) the render layer file is not denoised. Also you can check every render pass and look, what’s useful for your post processes like the common ones, clown, diffuse, etc. You can use the occlusion render pass or render your own, if you need more control.
Hope that helps a bit
CheerEO
Marco
P.S.: written on a mobile device in short form