Another step that helps is to do a Build All. Maybe the writers of the documents assumed everyone turns on auto-build. That seems like the most consistent way to get an update to show.
However, though your icons may show up in the palette, when you create an instance in your workflow, you might get a little red square instead of your icon. The only way I've found to fix that is to close the project and exit Eclipse. Upon restart and reopening the project, when you open the bpmn file... voila, the red square is gone and the correct icon is shown.