It’s always a good idea to read the manual…
Motion will have to analyze the whole movie file for the section you want to retime, so if you’re retiming a 6 seconds subclip of a longer movie clip then it will analyze every frame.
If the clip is only 6 seconds there should only be 150 (pal) frames to analyze.
Workflow is the following:
Set in and out points on clip to retime in viewer.
Select File: Export : Quicktime Movie
Make sure recompress all frames and make movie self contained are deselected
Import the resulting QT movie and drop on timeline
Set speed – deselect frame blending
Send to motion
Go to clip proerties, select timing: frame blending : optical flow.
Wait for it to analyze movie (a 6 sec clip takes about 8 minutes on my MB Pro)
Save and jump back to FCP
render and off you go.
Write 400 lines. “I will read the manual, I will read the manual, I will read the manual”
Good luck!