The method I use is to use a script, PowerShell, batch file, or whatever you want to call it to deliver to the Search folder a completed file. What I do is have the Download manager (using your examples) to copy the file to an intermediate folder first. The intermediate folder is on the same drive as the Search folder. Then when the copy to the intermediate is complete I give the command to move the file from the intermediate to the Search folder. Since it is a move on the same drive, it is instantaneous.
In my case I actually use a handy and free (for home users) program that handles the automation of the whole process called Febooti Automation Workshop. Automation Workshop (Free Edition)