1. Open Photoshop and type the text with preferably script font for sign effect. Draw the curved line below the text which we will reveal with animation.
2. Create second layer. Hide the curved line with white patch.
Concept : In the Dissolve mode, Photoshop will randomly change the layer pixels to 0% opacity and other will remain to 100%. This effect can be checked when the layer is set to the opacity less than 100%.