This is a great primer tube filler. I did some practice fills with it to figure out how much you need to slant the tray to get the primers to feed in the Channel and down the tube.
The videos are a good place to start. It will feed them fast if you take your time and do not let the primers make a traffic jam. Think of it like a pencil stream of water you want to run in the hole.
All I can say is that it works great once you figure out what angle you need to hold the unit.