WARNING
THE VIDEOS ARE WRONG!! DO NOT USE THEM UNDER ANY CIRCUMSTANCES
The videos are fine right up until he shows you how to judge the backlash. His method can and will damage your engine. To an Indian mechanic and customer the most important thing is NO noise at all. This is not possible with a mechanical thing, period. You can engineer in quiet but not noiseless. The downside of this fanaticism is wear.
Lets get to the point - Everything he says is right until he sets the backlash. What you want is to not feel any backlash when you turn the gear back and forth with your fingers, yet the gears should slip together easily and freely. It is a very fine adjustment and when you try it you will see exactly what I mean. No training, no special experience needed. Even the slightest too tight and they will not slip together easily. You might be able to get them to mesh but not easily. Any too loose and you will feel backlash. You must also check after you have tightened the lock nut. I also do NOT subscribe to his theory about making the adjustment where the pressure is the most. You should rotate the gear and check in at least three places to make sure that if there are any manufacturing variances they are taken care of. They need to be adjusted so that at the tightest place they slip together easily. Any other method will guarantee undue engine wear.
As a point of interest the way the gears are cut is quite expensive and help limit noise a great deal. It is also why the oil pump gear is plastic.