Using this plugin, in combination with the font manager admin tool, it becomes easy to use fonts in tinyMCE. Using the configured fonts list from the Font Manager, this plugin can be used to indicate the font to use for any selection from within the tinyMCE editor. Like most of us are used from any rich text editor such as Word or even Windows RTF editor, it provides a dropdown with known /confugured/installed fonts.
Be aware that the font must be known and configured from your Moodle installation. If certain texts are set to use a font that is missing in the font manager, be it due to removal or for any other reason, chances are high it will not be displayed. There is not much to do about this as no methods are provided anywhere in any way to detect and clean up messy code refering to fonts that do not exist from within your Moodle installation.