Cernocky

The Custom Post Styles plugin is an easy way to customize css of your posts individualy using CSS code. 
Plugin adds css editor box in your post editor.
See it in action: 
https://vimeo.com/179525212
Improve the user experience for your readers without having to change theme code.
<h4>Possible upcoming features</h4>
<ul>
<li>Better CSS editor</li>
<li>Custom webfonts</li>
<li>Supporting more post types</li>
<li>Custom styles for posts by categories, authors etc.</li>
<li>Visual editor</li>
</ul>

Custom Post Styles

Allows you to add custom css styles to posts.

rockgod100

Now fully compatible with child themes. Clone an existing template file without uploading new files via FTP. Optionally, a user can add a template name, so that the new file will be automatically recognized as a new page template in the post editor. If using a child theme, the new file will be copied from the parent theme folder into the child theme.

Theme File Duplicator

Clone an existing template file from the Wordpress admin area. Go to Appearance -> Add Page Template

Custom Post Styles vs Theme File Duplicator