The only way I know to do something like that is to group the layers add a layer mask to the group and paint on the group's layer mask .
Thanks for the reply
That isn't quite what I was thinking of. The more I think about it, the more I realise how kind of impossible it would be to use. The effect I want to replicate is when you lay down several layers of paint (we can just fill multiple layers with different coloured paint) and the you use a crumpled piece of magazine paper (or other) and lay it over the top the the paint. When you lift it up, it removes the layers of paint randomly depending on where you pressed and the crumpling of the paper....
I was thinking of a brush that you could setup which would erase the layers below it based on the opacity of any given part of the brush....Kind of like how a heightfield is generated from the gradients of an image.
man, I am not good at explaining things!
Yep, the more I type it and try to explain it, the more unrealistic it seems
Might be something that will always be done manually.
mmm as soon as I have time, I'll give it a go