Hoodedshivster talks about this method roughly three minutes into this video: Keep grinding, that glorious red beam of light is SO worth it. Pro-tip #2: Start teleporting to town while making gem upgrades to save a few more seconds. For instance, speed farming a level 60 GR, you would need to farm for roughly 2 hours to statistically see a Primal drop. The only difference in solo is that you may not be able to complete as high of level GRs in the same amount of time.

Solo speed farming works the same as group speed farming and the above Youtube link does an excellent job explaining the method. When your inventory gets full, unload it and move on. Pro Tip #1: Don’t spend too much time in town. Pick your best speed builds and GRIND AWAY! Remember you are focussing on getting the most loot possible to maximize your chances at a Primal drop.

The easiest and most fun way to farm Primals is to get together with a few friends and run through the highest level GR that the four of you can handle in around 2 minutes. Anthony Evans explaining Speed Farming Primals

Diablo 3 primal ancient