You don't have to do all that. Highlight the keyframed property. All the keyframes highlight. Right-click on one and use the Rove across time command. Now when you move either the beginning or ending keyframe on the timeline, the keyframes in-between move proportionately. Very handy for speeding up or slowing down.
I'm assuming you know how to turn a mask path to a motion path. If not here are the steps:
- Create a new layer for your mask path or use an existing layer
- The layer must not be scaled or moved out of position.
- Draw your mask then press Alt/Option + M then Ctrl/Cmnd + C to create a mask keyframe and then copy it
- Move the CTI to the point in the timeline where you want the motion to start
- Pick the layer or property in a layer that you want to move along the mask path (in your case Flair Center)
- Create a new keyframe for position Alt/Option + p or the position property of an effect you want to use and create a single new keyframe under the CTI and press Ctrl/Cmnd + V to paste the motion path to the property.
This should create rove over time keyframes for the selected position property starting at the CTI and ending a few seconds down the timeline.
Now just grab the last keyframe to adjust the timing of the move.
If rove across time doesn't work for your animation then you can select all of the keyframes then hold down the Alt/Option key and drag the end keyframe to scale the time between keyframes proportionally. I use this all the time to finalize my animation time.
Another option is to pre-compose your lens flair layer then use Time Remapping and adjust the timing there. For things like position changes you won't end up with blended frames. I hope this helps...