I had to do a bit of research when it came time for compositing in Nuke. I'm mainly an after effects guy, but this project required me to use nuke so I decided give it a try. Using the render layers made composting very easy as I was able to grade each light and then merge it with the other layers to get the desired effect. Desired effect meaning, Brighter highlights on the bottle, to better match the reference image, or to help smooth the ground and contact shadows. However, I was having a lot of issues with getting the color of reflections. Because I was in a time crunch, I had to fake the reflection pass a bit because I never created one for the shadows, so I used pieces of the scene to recreate to the shadow reflections.
The image for my blog post shows my workflow
First I took the initial BG image and colored graded it and darken it.
Then I mirrored the image over and manually placed it where the reflection would be.
Then I blurred it and merged it back over into the scene.
The I used the shadow pass I created as a mask to isolate just exactly where I wanted the reflections to be .