Multi dirty verts
From URCHN Arkipelago
Multi Dirty Verts
An add-on for adding dirt vertices to multiple objects
Use
For any number of objects, multi dirty verts will give them dirty vertices. Just adjust the pop up settings as you normally would for Dirty Vertex Colors and hit ok. Additionally, multi dirty verts clears all previous vertex colors before applying dirty vertices by default. That feature can be turned off with the Remove_Previous_Vertex_Colors check box on the menu.