It can be done fairly simply with behaviors. First determine the length you want for your transition. Let's say 30 frames for simplicity.
Trim all your clips in motion so they have 30 frames of overlap. There are several ways to do this, but this will likely be the part that takes you the longest.
Apply the Move behavior to the first clip in the slideshow. Trim it so that it's 30 frames long and at the end of the clip. In the behaviors tab, adjust the position so that the clip is no longer in view. Adjust the speed to Ease Both.
Copy the behavior by selecting it in the layers pane and hitting CMD+C. Then paste (CMD+V) the behavior to the next clip in the sequence. By default it will paste to the beginning of that clip. This is what we want. In the behaviors tab for the copied Move, switch the direction to From, and type the exact opposite number in the position box. In other words, if you moved the first clip 600 pixels on the X axis, then type -600 in the copied behavior. Essentially just add or remove a negative sign from the copy. This ensures the EXACT same speed and distance of movement for both clips, allowing one to "push" the other off screen.
Now you just need to copy those two behaviors to each clip of your slideshow in the same manner. When you're done, each layer except the 1st and last will have 2 move behaviors attached to it.
Hope this makes sense.
Andy
