When a transmission is completely dry, pump in trans fluid till there is excess overflowing (about 1-3 litres if i remember). Start engine (park only) this will circulate the new fluid in the trans pan to the trans, then keep adding fluid till over flow. Plug, don't crank the bolt. Put the car in Drive for 3-5 seconds, Reverse 3-5 seconds - repeat a few times. Keep engine running in Park after this interval. Finish topping off till leaks out. Wait till fluid warms up a bit 30-35°C More or less at 80-90°F. https://at-manuals.com/manuals/zf-5hp19/ Check out the link