Drainage is done from below
&
Refill can be done from below via pump which is the more advanced & safer way (which u saw in the video bcz it must be from abroad & they use pumps)
its safer as u there is no risk of spilling gear oil on paint or engine components
as a mechanic told me paint will be ruined wherever it drops
so only pour it after completely covering areas where it can spill
hope it helps
salaam