Make Black&White and Color Correct it then

I shot a little trailer un purpose in color (with canon 5D and 6D) to make it afterwards black and white. 

i did want to do in camera because it looks too flat and i was told there are more information to color correct then the black and white if i shoot in color.

does somebody know how the workflow is then to make it black and white and color correct it?

i would do it in avid itself.

or if have davinci relsove (i didnt use til now). 

thank you for your help***

fabienne