Exchange 2003 Offline Defrag

I want to perform an offline defrag of our Exchange database. It's currently at 69 GB, approaching 75 GB. This has happened before and we simply ask users to delete email in their inbox, sent and deleted items. I know about settinging quotas but it's meeting resistence right now. The article below talks about doing an offline defrag but I don't see anything showing a percentage or an amount of space I can hope to reduce my database by. Can anyone provide some information based on past experience? Also, does anyone know a good tool that can be used to drop each users mail into a separate .PST file in an automated fashion?
 
http://support.microsoft.com/kb/328804