In blender 2.73 I'm having an hard time finding the: "Add paint slot" button, i need this in order to paint my mesh interactively in the viewport. Here a picture:
are you in the texturing mode? have the object selected press tab (to select the object interaction mode) press 1 to go into the Texture Paint mode click on Add simple UVs - needed if there are no UVs yet. click on Add Paint slot create a texture and start painting. or better yet watch the great videos from XRG81 ;)…