Download the .fla file by clicking the link at the top of the swf, to see how it's done... 		Dross1 on the FlashKit boards asked if it was possible to make tracers (each of the last say, 5 frames fade out slowly, like onion-skinning in the development environment... Sure, why not...

See my "make Smoke" tutorial for how I created the other frames...
After I had my dupes. (I think I did 10) the only real trick was telling each duped clip on it's onEnterFrame to fade it's alpha based on 100/it's number, and telling it to go to and stop it's number of frames behind the seed clip... The code is pretty self explanitory, and I added a bunch of comments, so check it out, and see if you can't make it work for ya...

On frame 1 of the main timeline I put this code:

//create a function dupe() that takes some variables...
function dupe(name, howMany, depth) {
    //inside dupe, we make a loop that cycles "howMany" times you specify in the function call (below)
    for (num=1; num<=(howMany); num++) {
        //here we dupe the seed clip...
        duplicateMovieClip(name, name+"_"+num, depth-num);
        //here I set the alpha  based on how far along in the dupe process we are...
        eval(name+"_"+num)._alpha = 100/num;
        //here I create a tracking variable so the clip knows how far back it is in the sequence...
        //see the onEnterframe for the seed object for the rest of the code...
        eval(name+"_"+num).myNum = num;
    }
}
myDepth = 12;
//place animation at some arbitrary level in front of other stuff
anim1.swapDepths(myDepth);
//duplicates the movieClip "anim1" 5 times
//starts duplication from level of seed mc
dupe("anim1", 5, myDepth-1);

 

 

Then on the MC to be traced I put this code:

onClipEvent (enterFrame) {
    if (this._name != "anim1") {
        //sets each duplicated animation back by "myNum" frames...
        //you can tweak this to increase the frame delay if you like
        gotoAndStop(_parent.anim1._currentframe-(myNum));
    }
}