I reinstalled TS06 a few years back for repairing assets and the installation would die after a few days. No idea what the problem was but the database always seemed to get trashed. Don't remember the Windows version but it was probably 10.
After about three attempts I gave up. Curiously, the original Trainz, UTC and TS04 ran just fine apart from the clunky graphics.
As I recall, PaintShed only worked on diesels and the like. I tried a few times but it didn't appeal to me.
Assuming you are talking about PaintShed, or reskinning in general, the model needs a really simple UV map to make it easier to paint. Modern 3D modelling programs such as Blender tend to maximise texel density and the resulting UV maps are mostly highly fragmented.
If you can obtain an FBX version of the model then you can import into products like Substance Painter (expensive) and really do a good paint job. There are cheaper tools coming along.