all you need is a configured redirect server and to set your server cvar without a trailing backslash like this:

Code:
set sv_wwwBaseURL "http://redirecturl.com/files"
set sv_allowDownload 1
set sv_wwwDownload 1
set sv_wwwDlDisconnected 0
Then in the folder called "files" you would have folders like "etmain" where your maps belong, and "etpro" where etpro-specific downloads belong.