I have read lots of article on how to auto-version your CSS/JS files - but none of these really provide an elegant way to do this in ASP.NET MVC.
This link - How to
I usually append a fake query string to my resource files.. i.e
It doesn't require any url helpers and works no matter what's running the in background. To be honest I haven't throughly tested this method, but I've found it always fixes any resource caching issues people were experiencing.
You'd probably have to update the v=
manually, but it wouldn't be terribly hard to append a version parameter to the resources from a config file somewhere.
Edit:
I went back and throughly read through the content of the link above and realize you've probably already discarded this method. Apologies for suggesting it again.