There are several really detailed and well written posts you can search in the forums. Sergie (@thesergie) wrote a good post on CSS best practice that includes methodology and syntax and many people have written about how to manage and create global classes which I think are essentially what you are after for reusability.
Webflow converts all class names to all lowercase and replaces spaces and underscores with dashes (hyphens). Dashes are the recommended syntax for CSS (many JS libraries use camelCase). It also uses dot notation so your-class shows up in the CSS as .your-name
If you have a personal account or above, try exporting the code and looking at the published html and CSS - it will open your mind up to a great deal more to see how Webflow produces clean code and the methods and structure they use. If you are on a free account, you can still learn by using the chrome inspector on a published page.
Hope it helps. Remember to search the forums - tons of great posts on just about every subject - instantly.