I have a little add on to your method. Let me know if ya like it:
Put a horizontal split slide on the beginning of the single frame (one of which you took a snap shot of via Shift + N). Then export it by itself (obviously with same attributes as source sequence) & put it back in the sequence. Now, speed it up by about %500 and reverse it. Shorten it up so the clip is now only the duration of the split slide. Throw some opacity on it (hmmmm, I put %40 opacity) and place it on the video track above the original snapshot. Line it up right in the middle of the original dip to color dissolve transition, sync it with the shutter sound audio, and there ya go. I’m not claiming this is the best method, but figured I’d share my experimentation. Thanks again.
-jake