Last time I had a 308 out for a while I got a mates pressure pot filled with oil and primed it all first with fresh oil then run it picked it up good but have done vaso trick to pick it before an old 253 tonner I got once took a while and a few fills with a horse siringe ( from vet) through the pressure switch hole it hadn't run for years slowly started pumping oil up top when running put tapper covers back on drove it then sold it minus a few good bits