Another little cool thing that I use from time to time. This is a cool effect to use when you want to hide or show a billboard. You can of course make your own transition effects as well. It should work the same in a tracked compound but haven't test it. Let me know :)
How to use:
1. First right click your "Mixed Cam" or "Virtual Cam" compound and select Edit Compound In-Place.
2. Go inside the same compound, find "Input %N=1" and do "Edit Compound In-Place"
3. Go to Billboards tab and select Billboard 1 and "Go To Source Module"
4. Add my Billboard Dissolve compound between these compounds(right before the input "Keyed Video"
5. You may need to re-link the smoke video files inside Billboard Dissolve
Billboard Dissolve Template for Aximmetry