Last owner apparently not a big fan of changing the oil

I had a 300-6 in a Ford pick up that the oil pressure light would come on at idle when warmed up. After removing the valve cover all the oil was setting on top of the head. I pulled the drain plug and scraped and flushed with clean parts solvent. I removed the lifter cover too. Fresh oil and a new filter and started it for a few minutes. I drained the oil, changed the filter and did it again running it for 10 min. or so. Changed the oil and filter again. Finally I took it for a drive and did the oil/filter change again. That took care of the issue. Worked great. I worked at a dealership so filters and oil were cheap. But it did work well.