"I remember someone ( maybe KK) used to paint the slices "...

Yup. Good memory. Jus mixed with a little melted unsalted butter.
When I do parties where meats are served over a time span I cook several of whatever the meat in question is but only reheat/slice or slice/reheat one or two at a time. "Drying out" comes from too high a temp during reheating (allowing the meat to get too hot and thus start cooking again) or too high a temp during holding and service (same issue).