Using Manual Excerpts in Featured Article Box on Homepage

Currently, the BP Corporate Theme's Featured Article Box has two display modes:
1. Slideshow - Displays the featured image and an overlay containing only the post title.
2. Article - Displays the featured image and the first 125 words of the article, followed by a list of articles from the specified featured article categories.

How would I modify my child theme to display the contents of the custom excerpt field?

For example, when set to Slideshow, I'd like to display the post title and the custom excerpt. When set to Article, I'd like to use the custom excerpt instead of the first 125 words of the article.

Thanks