Scenario:
"I would like my blog to always use a certain skin, regardless of what skin is used in the blog settings."
Solution:
You can force Nucleus to always display a blog using a particular skin by adding a line to your index.php
<?php $CONF['Self'] = 'index.php'; include('./config.php'); selectBlog('blogname'); selectSkin('skinname'); selector(); ?>
blogname is the name of the blog you want to apply your skin to and skinname is the name of the skin you want to always use.
Further reading:
index.php are outlined in the article How to create a new weblogs on docs.nucleuscms.org