Slippery Primer tray
 

Maybe I'm the only one who never got the memo, but...

I've loaded many thousand shells over the years with a series of PW Progressives, and have always fretted over tapping, shaking and shaking the tray to get primers to flow into the loader.
Don't remember where I saw it recently, but just polished the primer tray with furniture wax. Problem solved. The primers now can't wait to get into line to go the loader.

Been using auto wax for years and lasts for months.