Vlad did not plan to stay with the battalion led by the 19 Bloodline Soldiers until every single one of them had sealed a Champion demon's soul in their hearts, as that would take too long, and he still needed to visit other cities.
The plan was to hand everyone a parchment with a demon-sealing runic formation and engrave the Demon Cage Runic Formation in their chests. That way, they could become Demon Soul Masters without the need for Vlad to be present.
Seeing that his orders were clear and that everybody was ready, Vlad led the forces of the 19 Bloodline Soldiers and the battalion to hunt down demonic hordes.
The 19 Bloodline Soldiers and the battalion had done a great job hunting down the demons in Trigun City the past six months, but there were still a few hordes left behind. Those were too powerful to obtain a flawless victory, and according to Overlord's plan, it was better to wait for the soldiers to grow stronger before challenging them.