Probably depends on model but I did it solo. I built a back rivet jig mounted to my hydraulic floor jack. Took forever but it worked. One rivet at a time. Packing tape. Place the jig with a tiny bit of pressure. Bang. Lather rinse repeat.
For the center section bottom skin I stood the whole center section assembly upright on the spar carry through, and riveted it while it sat vertically. For the tail cone I backriveted the bottom to the sides.