Simply use the TurkPrime "Restart" feature which Restarts HITs that have become sluggish. When you Restart a HIT you get the effect that it gets "bumped up" the Worker visibility as if your HIT just started.
When using Restart, Workers who have completed your original HIT are automatically excluded from taking the newly created HIT and are unable to accept the HIT because TurkPrime has created a Qualification Type that excludes them.
There is nothing that a Requester needs to set up to enable the Restart feature. It appears in the TurkPrime Dashboard as soon as your HIT goes Live.