In general most software packages,  allow 5 distinct methods of working with textures. 

1. procedural
2. implicit
3. planar projection
4. cylindrical projection
5. spherical projection 

 

To accurately paint and texture your model when using projection mapping, you will need to understand and overcome the problem of texture stretching.         The key to this, is to remember that when textures are projected, they are actually shooting through the model  (see figure to the left)

To avoid this, put the object in a "paint" shape so that the projection will not stretch, then apply the texture to the object and return it to its original position.