best way to use the clentaminator to fix a whole world in terraria

Do it in long horizontal passes rather than chasing the biome around. Dig or blow out a few straight tunnels through the infected area first (or reuse your hellevator for vertical bits), then fly or ride along them holding the spray. The spray changes blocks in a wide band around the line, so a few parallel tunnels clean a whole section. Green solution is the one that purifies, the Steampunker sells it in hardmode. Buy a lot more than you think, a whole world eats hundreds. And build a gap of a few blocks around anything you've cleaned or it creeps back.