So I do a lot of layering work on my renders - generally to add backgrounds without adding massive render times - and, thanks to the alpha channels Studio automatically creates with .png files, this is pretty easy. But I do have one reoccurring problem that frustrates me. Inevitably the top layer has a thin line of white around the added content. Usually it's not enough to bother me much, but when rendering hair the problem becomes extremely visible -- a large white halo around the character's head that I have to go in and fix by hand.

Has anyone found any tricks for getting around this issue?

Change the background color in Studio so that it is
close to the color of the background you are going to end up with.
or use a black background in studio.

Can't speak for Paintshop or GIMP but in Photoshop the layer matting option allows you to remove the white. It cleans up layered images really good.

I am too cheap for Photoshop; I use a Mac version of the Gimp, and there doesn't seem to be that option anywhere. Oh well, cheap strikes back again. Changing the background worked though. Smart girl, never realized that a backdrop wouldn't get rendered... headdesk Thanks guys.