The SM is inverse masked, masked, masked, unmasked, and painted; the S-IC fin fairings are, too (roughly).

The SM is silver; there are several white radiators around the SM, some near the top edge, some near the bottom. The top radiators are fairly small, and there are lots of them. The SM was painted white, like the rest of the model: the base coat. In order to mask off the top edge radiators, I masked around the radiators and applied a few coats of liquid mask, then unmasked after it dried. While it dried, I masked the bottom radiators. This evening, I painted.

As to the S-IC fin fairing, I also used liquid mask along the top border of the silver, after unmasking from having painted the black roll pattern. I als peeked a bit, and unmasked a little bit of the roll pattern on the S-IC/Interstage/S-II.

I remasked. As to the fin fairings, I had cut pieces of tape (one per fairing) to mask the silver part at the bottom of the S-IC fin fairing. I wanted the base coat beneath the silver to be uniform: all white. This gave me a nice guide line for the top edge of the silver paint. Again, a few coats of liquid mask took care of things; after it dried, I removed the tape covering what will be the silver area.

After painting: