Hi,
The help topic is definitely there. However i don’t think decals is going to be the solution.
Since you only want line art, try the following.
The hardest part is dealing with the pinching at the poles.
One way to deal with that is to work on a bitmap cubic map and then convert that to an equirectangular texture. Then trace that to get the line art. There are a few free online cube to equirectangular converters out there.
Or if you do a lot of this then I recommend Flaming Pears Flexify 2 plugin for Photoshop.
Hope that helps, Steve