Growing Lichens on rocks

I read somewhere that painting yogurt on rocks will hasten the appearance and speed the growth of lichens. I tried doing this in the summertime but still have no results. I had a forgotten quart tub of plain yogurt in the frig that had a bit of mold on top but didn't smell "off". I diluted this into a watery consistency like some of the yogurt drinks you can get now and painted it on a lot of rocks. Nothing. Maybe the heat and full summer sun dried the yogurt too quickly or the coating may have been too thin but there is no evidence of lichens or moss.

Today I went out again with brush in hand. Since it had just rained last night I thought the yogurt wouldn't dry so quickly and I used it full strength this time. The rocks look weird with white streaks slathered on top and on the sides. Now we have fog so hopefully lichen spores (?) will have time to land on the yogurt and establish itself if indeed that's the way they propagate. I need to do some research on how lichens grow. Will report back later.