Snapping FK to IK for whole action instead of single frame

I used Blenrig 5 to rig a character. I am applying a mocap animation to it. It was succesfully done. Now to cleanup the data, I want to use IK legs. Since mocap data is applied to FK bones, I need to switch to IK bones. In blenrig, there is an option to snap FK to IK for current frame but not for whole sequence. I tried baking animation too. Is there a script to solve this? or any other way?