With Critical Fonts feature you can select icons that you are actually using on your site, and generate customized icon font set from them. There is also a feature to search used icons in your theme/plugins, posts, options, etc.
Once you selected the icons that you need, you can enqueue them with one click. If critical icon fonts are enqueued, the plugin will block the original version of the font CSS/font files.
Critical Fonts supports Font Awesome 4.x