Source: extension.joomla.org

My greatest disappointment was to open my JCE content editor for testing expecting to find my uploaded fonts as available selections. Not so. I guess they must all be defined through the supplemental style sheet. Experimenting with fonts is a trial and error process and it beomes tedious when they must be applied through a style sheet. Plus I would like to have the option to applu a new font to selected sections of text only. If this extension can do that I do not know how and therein lies the problem.

Answer:
This is not a pcDTR thing to fix. Someone must write a plugin for JCE that fixes that.
And i don't know how you use to handle JCE, because you always need to create a css first. Yes that's a tedious jobb.

And yes you can apply classes from JCE. This can easily be solve it if you read a little about JCE. You can add custom css to JCE.

So what you need to do is creat a dummy css file. With the same classes you have in your styles.css. And then you will have them in you JCE styles list.

Example:
If your styles.css looks like this:
.contentheading {
font-family: Brody;
font-size:18pt;
color:#C60;
}
.contentheading a:hover {
color:#06F;
text-decoration: underline;
}

Add this to your templates/$template/css/editor_content.css:
.contentheading {
font-family: Arial;
color:#C60;
}

Remember Google is your friend Jce Editor Custom CSS file