[rc4flying]

Plus, one other thing I forgot. I only spend the extra sanding effort on the side that will be showing when done. The glue side of the sheeting, I just make sure there are no major glue drops or offset seams to interfere with the glueing to the cores. Heck, 150 is good enough for the glue side. Besides, you want to leave some wood so you can give the showing side a good sanding job. Also, vacum the wood often or otherwise you are sanding balsa dust over and over.
Again, Just my way of doing it.