You always need Nitrogen. You just want to deplete it during the finish.
If you want to bring the Nitrogen level down; You delete Grow from the equation.
The GH equation to use would be 0-1-2 parts. 0ml Grow, 5-8ml of MIcro, 10-16ml Bloom per gallon. I recommend you use 8ml Micro, and 16ml Bloom