Better Snap Image

[micheus]

That's the right way to do what you were looking for.

I think you (in step 4) can select all the faces you want to assign the image and in the AutoUV Segmentation you select those faces and after change to Edge mode [E] you Mark all them for cut. Next, you continue the process using the projection normal.
Now, in the AutoUV Editor you select all object (islands) and center them. You also may want to scale uniform max.
At this point you even need to use the Create Texture option. The mesh already has the UV information and you can close the AutoUV Editor window, so you can just assing the material as you do in (5).