Well... Blender is giving me the most flexible approach.
I set the camera and then paint the texture.
Any solution involving geometry projection would make editing (change of position, change of texture...) painful.
I considered buying Blendup (a Sketchup to Blender transfer add-on) to import my Sketchup cameras and geometry to Blender, paint in Blender and back to Sketchup.
Eventually, I chose to do everything in Blender (model, texture and render).
I will let you know how it turned up!
Thanks a lot for your help, gentlemen! π