Paint Toolbar and Palette

The Skin Painter is a basic painting utility to add texture to your model. While normally you'll use an external paint program to create your skins, the Painter has all the basic functions you need to quickly create or modify skins for your models. It is activated by clicking into the 3D Painter window. You can rotate the model through the sliders, and paint directly onto the skin.

Select If activated, you can select triagles by clicking into them or drawing a frame around them.
Move Moves all selected triangles of the skin mapping with the mouse.
Rotate Rotates all selected triangles of the skin mapping with the mouse.
Scale Scales all selected triangles of the skin mapping with the mouse.
Restrict Restricts the Move / Rotate / Scale direction to the x or y axis.
Mirror Mirrors the selected triangles.
Weld Welds the selected vertices together.
Detach Detaches the selected triangles from each other.
Selection only If activated, only the selected triangles are visible and can be painted.
Color Picker For picking a color from another part of the image
Pen Draw/Paint on the skin in the 2D window with the selected color.
Fill Fills the whole triangle with the second color, and the triangle border with the selected color.
Fill Selected Fills all selected triangles with the second color, and the triangle border with the selected color. You can also use this mode to export the mapping with the skin image.
Palette

For selecting the four available colors. The selected color is the line color, the second color is the fill color.

Do not forget to recreate mipmaps after having painted onto the skin. Otherwise, your painting would only influence the first mipmap and fade out in the distance.