If you are looking for a simple, but rewarding way to grind focus, this solution is for you. Three main points will make this grind easier for you- Excalibur, max rank. As many energy restores as you can make, because energy leech is a pain. And a sortie with survival, hopefully eximus stronghold. Do not do this solo or you will spend all your time going through energy restores. Your goal is to save your energy for a focus amplifier, and then unleash exalted blade on enemies 60+. Per amplifier (45sec) i averaged between 6-8k focus. Per mission, about 25k for a 10 minute survival sortie mission. What you do between amplifiers is up to you, but during that 45 second stretch, find a long hallway, turn your camera to the door, and move left and right while swingong the exalted blade. Stand as far as you can from the door to avoid energy leech. Happy grinding, Tenno.