this can actually be a complex problem and may have many dimensions:
Please define further: Are you developping locally (server, DB is on your computer) or remotely (Hosting, FTP, etc.)
Caching can be really a bitch:
The WebHosting may have a Cache mechanism working (e.g. Varnish Cache)
The Wordpress may have a Caching mechanism (as e.g. W3CTotalCache)
With the Browser Cache you have set a long Caching for css files (.htaccess)
So if you have a good htaccess setup etc. all three caches should make it harder to refresh (specially) css changes.
As mmm pointed ot, to include the version in the functions.php is a very helpful and recommended method, but doesn't always work (for example Varnish Cache)
So if you're in development, it's recommendable to turn off al caches while you are doing css changes, and stay with the "version number refresh", it's the most recommended method.
If it's already a production site, I recommend you to get used to empty all three caches before the refresh (for a few changes it's no problem).
But there's no easier way, that's what caches and long-lifes are for.