ambient occlusion layer as a mask?

ok so i had this idea.
i want to grab the AO layer (may be over do it) and use it as a mask to paint dirt and rust in to the corners and all the crevasses in my mesh.
but i can t see any way of getting the AO layer in the texture nodes.
if i was doing a still i could just save it to a jpg then bring it back in as a texture. as long as i do not move the camera that should work.
but is there any way to get it in the texture nodes?

so i got the idea from watching a demo of luxoligy. at 8:20 in this video.

i know in this video he is using a paint. i don’t need to paint.

any way i will keep playing but if some one has one ideas that would be cool.

Unwrap your mesh and bake the AO, and use the baked map as a stencil.

every time i bake the AO it says no object or images found to bake.

got it to bake had to add a blank image…

ok that gave some crazyness… this is a screen shot during the bake. it starts out fine and then goes crazy. any thoughts.


btw the un wrap was of some simple shapes on a cube that i unwraped nicely.

bevel modifier did it… i had the bevel turned on… turn it off and bam…

wow that is cool i will have a long look at it when i get time. it is close to what i want to do.
any thoughts on rivets and weld lines