To be able to display previews for Adobe Flash files, Soufflé must be running. You can check “Start Soufflé on system startup” box in Preferences to avoid launching Soufflé each time manually.
Once you click on a Flash file in Finder (no need to open the file), its preview will be generated:
Additionally, movie info becomes available to you.
Note: If Flash files are stored on mapped network drives and drives on most network attached devices, which are connected to your Mac via SMB, AFP, FTP, NFS, RFS and other file protocols, files’ info (like dimensions, duration, etc.) may sometimes be unavailable.
To change the movie moment for creating the preview, go to Preferences: