Finger drawing effect

[AlbertGalka]

Dear Magicians.
     Could any of you give me a hint on how to get the following effect?

There is an inscription on the rock. The finger draws the rest of it (it doesn't exist) and the drawing is created.

Please take a look at the video clip to see what I mean.

Best regards.

[Rick Gerard]

• Start here:
  1. Pick a frame near the end of the video when the hand has finished drawing the path and save the frame as a Photoshop Layers file and put a marker on the layer on that frame
  2. Add a new layer to the Photoshop file that contains only the new part of the inscription using blend modes or clone and color effects until you get the look you want
  3. Motion Stabilize the video so that the rock does not move
  4. Import the PSD you created from the frame choosing only the new layer, move to the marker and then copy and paste position, anchor point, rotation, and scale from the video to the inscription layer
  5. Add an animated mask or an animated shape layer above the inscription that follows the path of the finger that you can use as a track matte to reveal the inscription
  6. Add a new null to the comp
  7. Rename the footage layer stabilized
  8. Move the Time Indicator to the first frame of the comp
  9. Add these expressions to position, scale, and rotation if you have motion stabilized with all three properties
     

     // position
     thisComp.layer("stabilized").transform.anchorPoint
     
     // Scale
     x = value[0];
     y = value[1];
     tx = thisComp.layer("stabilized").transform.scale[0];
     ty = thisComp.layer("stabilized").transform.scale[1];
     nx = x/tx*x;
     ny = y/ty*y;
     [nx, ny]
     
     //Rotation
     - thisComp.layer("stabilized").rotation​

  10. Parent the footage layer, the inscription layer, and the track matte to the null to put the camera movement back in the shot and add it to the track matte that reveals the inscription

No plugins are required, just motion stabilizing to make it easier to do the rotoscoping required to reveal the inscription and make sure that the inscription is locked to the rock. This will work even if the motion stabilizing isn't perfect. By far the hardest part is creating a believable inscription layer in Photoshop. I would save those expressions as an animation preset. I probably use this technique a couple of times a month and have done so since you could save animation presets.

[AlbertGalka]

Dear Rick,
I don't know what to say...
Thank you so much for such a complex explanation!!
Best regards!