Most of this tutorial it's explained on the action script code.
New Document
Clic the icon on the top right corner of the library panel and select "new Font"
Name: fuente1
font: choose any font you like. OK
Right clic the font in the library. > linkage > Export for actionscript and export in first frame
identifier:fuente1
Now, select the first frame, open the actions panel (window>actions) and paste these actions:


//set the initial position of the textfield
xinicial=100;
yinicial=100;
//set how many textfields we will make
cantidad=6;
//what we want the textfield to show
frase="efecto texto";
//set an style we are going to apply to the textfields
estilo=new TextFormat();
estilo.font="fuente1";
estilo.size=30;
//how much we are going to allow to move to each textfield
flashe=4;
//a variable we're going to use in function mover
k=0;
//this function will move the textfields
function mover(){
//increases k in 1 every time the function is called
k++
//every 50 times the function is called...
if(k>=50){
//if it is between 50 and 55...
if(k>=55){
//if it is greater than 55, we set k again to 0
k=0;
}
//we increase a lot much this variable
flashe=3*k;
}else{
//if it is not between 50 and 54, the variable will be always the same=4
flashe=4;
}
//this is what makes the textfields move
for(i=1;i<cantidad;i++){
numerin=Math.random();
//this is in order to allow the textfields move in any way (left or right and up or down)
if(numerin<0.5){
sentido=-1;
}else{
sentido=1;
}
cp=this["campo"+i];
//set the x and y coordinates using the variables flashe (how much it can move) and sentido (in x, -1=left, 1=right, in y, -1=up, 1=down)
cp._x=xinicial+Math.random()*flashe*sentido
cp._y=yinicial+Math.random()*flashe*sentido
}
}
//creates the textfields
for(i=1;i<cantidad;i++){
this.createTextField("campo"+i,i,xinicial,yinicial,1,1);
cp=this["campo"+i];
//display what we want the textfield to show (we defined that variable above)
cp.text=frase;
//apply the style to the textfields
cp.setTextFormat(estilo);
cp.embedFonts=true;
cp.autoSize="left";
cp.selectable=false
//set diferent alphas for every textfield
cp._alpha=i*100/(cantidad+1);
}
//creates a movie clip that will call the funcion mover()
this.createEmptyMovieClip("acciones",cantidad+1);
acciones.onEnterFrame=function(){
mover();
}



Now go to Modify > Document and set the Frame rate to 30. OK
Now test the movie!
you should end up with something like this: