for some simple use cases you might would like to take a look at link below.
Basically it's a custom css manager that can:
1) group styles and you can reference them by group name
2) cache on server and client
3) handle PerformSubstitution property.
4) minify stylesheet using AjaxMin
Currently it's the way I see to work with current Telerik controls, if you have turned off skins and embedded styles in web.config and would like to preload (if you are dynamically loading Telerik controls you will want to do that, otherwise some styles or resources might be loaded) everything (with server and client caching), also load styled RadEditor dialogs (if you have turned off skins and base stylesheets load in web.config for Telerik controls, e.g.: RadEditor's dialogs will not be styled when loaded).
Note that my goal was to preload customized LinkManager with styles, for other dialogs you will need to add proper references.
Note: my WebApp doesn't use skins
Article is here: http://weblogs.asp.net/evovision/archive/2011/10/09/implementing-a-custom-css-stylesheet-manager-and-taking-advantage-of-caching.aspx
P.S.: copyrighted by all .NET developers :)
P.S.S.: it was developed using coffee with milk and desire to go to bed earlier, so don't question code quality :)