ageing roughcast render - cow manure?

[countrycottage99]

I have a new extension covered with roughcast render attached to a cotswold cottage - I want to encourage moss etc to grow as it looks too new. Does anyone know if cow manure or yoghurt will work, and how I would go about it?

 

[Possel]

But moss will help to make your wall damp... Presumably you'd like lichen on it to have that weathered look, so I suggest you just wait a few years rather than interfering with nature!