Hi there. In actual fact I have two workflows and it depends on the project. One is designed for faster turnaround and generally lower budget and for those I simply use the colour tool within FCPX and sometimes use the vignette filter as a faux power window. And the other is FCPX > export XML > RESOLVE . import xml. From there I can go straight out or export xml for FCPX back into FCPX. As a rule any VFX shots get pulled from FCPX into AE and the only grading I do there is simple blending so everything looks part of the same scene.
If you dont have resolve abd you don't want to spend the $$, you can download resolve light free and its still quite powerful. I used resolve light for a month first when I transitioned from Apple Color.