It’s easy to add a Scribble Effect to a whole object. Just select the object and go to the Effects menu > Stylize > Scribble. In the options window that opens, select one of the setting Presets from the popup menu at the top of the window as a starting point. Then customize it to your liking and click OK to apply.
But how do you apply this Scribble Effect to just a Stroke or a Fill of the object? Ah! That’s where the Appearance palette comes in. It’s kind of like the “Layers” palette of Effects in that it shows all Effects that have been applied to a selected object and in what order. It also allows you to choose what part of the object (Fill or Stroke) to which an Effect will be applied. To apply an Effect, such as a Scribble, to just the Stroke of a selected object, simply click on the Stroke listing in the Appearance palette and apply the effect in the Effects menu. After the effect is applied, it is listed in the Appearance palette, under the Stroke listing, so you can alter it at anytime simply by double-clicking on the Effect listing.
Tip provided by Jeff Witchel, Certified Adobe® Training Provider.