Importance of FK and IK

Since I started learning about 3D animation, I've always been aware that FK and IK handles are very important.

IK handles basically mean that the point will stay where it is and everything will move around it, an example being a foot on the ground; you don't want it to move about as the character tilts forward.

FK handles are good for when you want a point to move around freely, such a waving arm.

My problem was that without thinking about it, I decided to suddenly switch from FK to IK handles on the character's hand when he rested it on a door. This resulted in horrible in-between frames when I flattened the tangents in the graph editor.

I'm currently looking into smoothing out the animation with built-in Maya tools, but I will most likely have to re-do all of the hand animations I've done thus far.