Every 3d-artist has at least heard of ZBrush or Mudbox. There is something equal for AM too called 3dPainter.
In difference to ZBrush and Co. it handles the native A:M fileformat and can be activated by plugin from A:M. With this plugin it is possible to start 3d-Painter and to hand the model over to 3d-Painter. Now you can edit the model in 3dPainter, save it and get it back to A:M to work on.
3dPainter is developed by Pixosaur (www.3dpainter.com)
3d Painter is not the solution to all the texturingproblems, but it can help very much in some complex areas of texturing.
It is not possible with A:M to insert new polygones / patches, so micromodelling is not possible, but the displacementmaps and color-map-options are astonishing well.
For less than 100 dollars you get a tool that does exactly what it promises, even so it doesnt offer all the possibilities like for example ZBrush.