Lumbrales

Hey, I'm completly new to editing with this particular program. And I the exact same issue as this thread: http://forums.getpaint.net/index.php?/topic/17832-gradient-tool-and-layers/ The problem is that even though I have the help of that thread I still can't figure out how to fade the edges in the way I want to, I can fade them one by one in each layer and then select all, but the result is very unsymmetrical, and the fade effect starts to late and it's in too much quantity.