Hmmmmm...............I can't remember what I did last time but I believe I grouped everything together and tried to do this but it didn't work. I think I also rasterized/flattened the image before I did that as well so maybe those could've played a part in that mistake. So when you say "group everything" do you mean the sub-groups of layers (hair, face, clothes, ect) or the ENTIRE file like I did?
And I assume you mean the layer styles gradient overlay right, not using the gradient tool? Because if that's what you meant that was probably my BIGGEST mistake--using the gradient tool in the bar, not the layer action that's a part of the blend overlay and inner/outer glow and other stuff.