Technically, the mo-cap BVH format would be a way to bring bone motion back into A:M
Some people have used the MDD point cloud format to move animation between A:M and elsewhere but I have no idea how that works.
The part I bolded sounds like a needless complication, unless you totally LOVE the other 3D paint program you are going to.
What i like to do is wrap my model with a blank image map, then take the model to 3DPaint to sketch in the major landmarks. Then I take the bit map with those major placement clues to a 2D paint program to do the careful detail work.
My model stays A:M, no conversion hassle.
I did my Al Capone head that way.