I didn't have time to read all the new posts on this thread just skimmed over it so forgive me if I read wrong, but you can definitely draw on a globe in 3d in Photoshop and it's really easy to do, it's also a quick way to check the poles without having to switch to another app. Just make a merged visible layer at the top of the layer stack then with that selected hit the 3D tab at the top, then press new mesh from layer then from the list hit mesh preset, and then sphere. It will ask if you want to enter the 3d work space hit yes and then you can see you're equirectangular map on a globe and navigate it in 3d space.

From here you can choose a normal brush and start painting, when you're happy with how it looks on the globe go to where you're layers normally are and you'll see a 3d layers tab, under it hit sphere_material. Then at the top there will be a properties tab that sais materials just under it then under that it sais diffuse, then right beside diffuse there should be a tiny picture of a dog ear'd page with a few symbols in it, it's very small, click it, then a few options will appear so choose edit texture and the 3d image will be projected back to equirectangular.

Be aware that the image will be opened in a new document, I find this helpful though because then I don't screw up the original and if I like the changes I just drag it back onto the original image.

I hope that made sense, I think I posted how to do it with some screen shots of the process over on PaGaN's thread so I may have explained it better there. I had a few too many with christmas dinner tonight so I'm not sure if any of that will be helpful or just utterly confusing... I guess I'll find out in the morning.