I went to see the Norman Rockwell exhibit at the Crocker Art Museum and...wow. The guy could paint. Here's a list of observations about his paintings and technique (note, these are my own personal observations from memory and have not been fact-checked.)
The paintings are much larger and way more textural than I had thought.
On some, he appears to have used a thick gesso prior to starting the painting.
He used a variety of canvas weaves - some were miniscule, others were nearly as heavy as burlap.
He really varied the amount of detail used in each painting. Some areas of lesser importance were left nearly as underpainting washes, while other areas such as faces were much more finely rendered and also had more paint.
He used paint thickness to advantage. On white highlights, he built up the paint. The miner's light in "Mine America's Coal" is especially thick. Also, in The Art Critic, the paint on the palette is built up as it would be on a real palette.
He uses a wide variety of colors to draw the eye. In Girl at Mirror, her dress is made up of light blues, yellows, and pinks. There is a tiny dot of cadmium red (?) at the join between her shoulder and the dress, apparently solely to draw the eye. This is again seen in a couple other areas of the painting too.
Several of the paintings had dedications in the corner, apparently to people he presented the paintings to?
There was a certain blue-green color that he used in paintings over and over again.
Often the charcoal lines were very visible and added to the final impact of the painting.
In one painting, a newspaper's lettering was rendered so small and so finely that I wonder if it was done in ink rather than paint?