Hi
Either way you will have to work on each inserted or overlaid clip. You can speed up the process quite a bit however and still acheive what you want..It just needs a bit of prior work. :-) here is a reply I posted to a similar question some time ago........
###################################################################################
You have complete control of fade-in and fade-out of any clip/image placed any track.e.g. Place a clip/image on the Track in question.
Click the FX button and choose the Transparency effect. Now click the Select Preset box and choose the Fade In and Out option.
When you now click the keyframe graph button (green cross with the red line around it) you will see the fade in and fade out graph line........

This is a little abrupt as it is simply fades IN and OUT and as it stands it doesn't retain the image for any time at 100% opacity before it fades out again. But you can easily alter that. Grab the line just after the start of the clip (e.g. a couple of seconds in) and pull it straight up to the top. This creates a keyframe and the Fade-in now happens more quickly and the clip remains visible for longer. Do the same a short time before the end of the clip.The graph line should now look like this.....

It is up to you to decide where to pull the graph line up.
In this example the image/clip lasts for 10 seconds and will fade in for about 1 second from the start and fade out about 1 second before the end.
##################################################################################
Once you have a decent fade-in and fade-out interval selected you can save it as a new effect. Click the 4th icon along at the top of the effects pane (looks like an old 3.5" diskette) and give your effect a name, then save.
It will now appear at the bottom of the effects list when you click the green cross under the heading Templates. You can now use this as an effect for each of your overlaid cutaway clips
Nat