Thats exactly right. In Iconographer, I recommend you work in the Thumbnail and Thumbnail mask views, and use the "Complete Icon" command to generate the lower resolution views. Then, you can go to the lower res views and tidy them up by giving them a slightly simplified icon.
For example, say you want an icon that is a sheet of paper with a flowchart-diagram on it, you would draw this in Thumbnail (128 x 128), then generate the mask. Then, edit the mask if you wish, I usually do a little mask editing to create a slight shadow and softer edge.
Then, uses "Generate Icon" to automatically produce the lower res icons. Switch through these and see how they look. At some point, the detail will become a meaningless blur, so you edit this icon to something that still makes sense and looks almost the same. In our example, we might make the smaller icon a sheet of paper with a single flowchart symbol on it. That way, in list view you still get a clear and meaningful icon.
SHADOWS are created by making a black area on your icon, matched to a grey area on the mask. GLOW such as lens flares are created with white on your icon and grey on the mask.