If you are using TRS2006, 09 or the TC series, my suggested approach is to use CMP/CM2 to find the asset, Open for Edit in Explorer, and move the folder containig the asset to a temporary folder outside the TRS folder.
Open the config.txt file and change the kuid of the asset to a kuid2 format.
For example, if the original is kuid:123:456, change it to kuid2:123:456:1. When uploaded to the DLS it will then automatically superceed the earlier version.
If you need to update again, just go to :2, then :3, ... .
If using TRS2004, this process can be done using TrainzObjectz.
Phil