Texture painting with layers and multiple uvs

hello i have been asked to modify a low poly armor for a game and had to change one part of the original model.

So i went on and separated the object into 2 meshes , baked the ambiant occlsuion and i wanted to try a new method that i saw in this video http://www.youtube.com/watch?v=1iy3pck8gz8
instead of exporting to gimp I wanted to set the ambiant occlusion as a multiply layer directly in blender and paint on the 3d mesh but somehow I’m never painting on the right layer even if the brush symbol is on the right layer it doesnt paint on it ( im using a special addon called texture paint layer manager.

DOes anybody know why it wont work here is the blend file:

http://www.pasteall.org/blend/24175

Also is it possible to bake the ambiamt occlusion of just a vertex group?

Sorry to bump the topic but being able to texture my models with multiple painting layers in 3D is a really important milestones on my road to become a better blender artist!

So please if you know the solution to my problem or my mistake answer me!

thanks for your time

Yes, to fix your issue you need to tab into edit mode, and with your mesh selected and uvs in the 2d Image Editor, switch the image view to put them on the image referenced in that texture slot you called “change” and then tab back to Texture Paint mode. You can then paint on the image “change” and not affect your AO image.