>>543649690
You literally just feel it out and pay attention to the revs either by looking at the gauge or just listening and feeling for the range you know the car likes to shift at and get good with the fancy footwork to manipulate the clutch plate and motor itself while shifting with your hand and holding the steering wheel with the other.
Basically you just get your legs and arms working independently, together, and with minimal thought and you'll be driving smooth.
Starting from a stop, especially on a hill without any of the modern hand holding technology they have in manuals now, is the only kind of difficult part and even on a hill you can just engage the E-brake and drop it as soon as you get into gear and start overpowering the break.
I grew up on 4 wheelers and snowmobiles and dirt bikes so I already was familiar with a lot of driving concepts before I ever got in a car or dealt with clutch pedals. It all came pretty naturally and I enjoy driving for enthusiast reasons which gave me a lot of practice.
That or do the weeb thing and read a manga that goes into autistic detail about driving.
https://www.youtube.com/watch?v=HIvAMc0ZX0Y