[snookca]

Read through smacss.com, if you haven't already. It advocates a modular approach that should minimize the impact that components have on other components, thus a style change to one component won't blow up the rest of the site.

Third party tools can be hit and miss. Hopefully you're working with plugins/libraries that don't inject inline code and rely on namespaced classes to achieve the result you need. Then, you have control of the CSS to style as you wish.

(disclaimer: I wrote smacss (but didn't write the blog post))