MC follow another MC, PERFECTLY!

[Nig 13]

Hi, it's been ages since I've been here. Hope to get some answers, as this was the first flash forum I got to know when starting with Flash

So I've like searched the WHOLE internet (just kidding) to find the solution to my problem. Due to the disappointment, I've been led to ask this question myself.

So, I have this Movieclip with these movements:

onClipEvent(enterFrame){
    if(Key.isDown(Key.LEFT)){
        this._x -= speed;
        this._rotation = 0;
        _root.axe_mc._rotation = 0;
    } if(Key.isDown(Key.RIGHT)){
        this._x += speed;
        this._rotation = 180;
        _root.axe_mc._rotation = 180;
    } if(Key.isDown(Key.DOWN)){
        this._y += speed;
        this._rotation = 270;
        _root.axe_mc._rotation = 270;
    } if(Key.isDown(Key.UP)){
        this._y -= speed;
        this._rotation = 90;
        _root.axe_mc._rotation = 90;
}

And on the walls (this is only for the Right-side wall):

onClipEvent(enterFrame){
    if(this.hitTest(_root.hero)){
        _root.hero._x += 5;
    }
}

I want the hero movieclip to change into different costumes, but if I do that, it will also affect the Walls. If I make a costume, LARGER than the movieclip, or even smaller than, the hero movieclip won't be able to move as freely... You get it, right?

In order to prevent this, I made another movieclip, and will make the costumes there. On this movieclip, I have put this code:

onClipEvent(enterFrame){
    this._x = _root.hero._x;
    this._y = _root.hero._y;
}

Working good, but the only problem is, this costume movieclip's _x and _y aren't 100% following hero's _x and _y. I know of updateAfterEvent(); but that doesn't work. According to myself, updateAfterEvent(); only works when using onMouseMove, true?

Anyways, how to make the costume movieclip follow the hero movieclip, SMOOTHLY and PERFECTLY? Because, this follow mc script is ruining the Wall hittest ;(

Thanks in Advance