It just takes lots of practice. As you get more familiar with the clutch, you'll know when it starts to "bite" as you let it out, and you need to add throttle to compensate.  Once you let the clutch fully out, the engine and transmission become one unit, and you can't brake again without pushing the clutch back in, or the motor will stall. It's not like an automatic, where the torque converter can freely spin in hydraulic fluid if the car isn't moving, and the engine is running. I've only driven a stick a few times. I did it on an at-the-time brand-new 2018 Mustang with the hill-hold feature and I'd stall the car. My mom had to practice learning to drive a stick in the Black Hills of South Dakota. She says I have it easier than she did, because of the hill-hold feature. I think it's the opposite, I think I'd prefer to not have the hill-hold feature so I can gauge the engine's "bite" on the clutch better. As you let out the clutch on an older car, you can feel the engine strain, so you compensate by adding more gas. I didn't have that option, and I frequently stalled the Mustang on hills. Once I got it going, I was into it. Having to change gears yourself is a lot more fun than a transmission that does it for you. I know all about torque and horsepower at specific RPMs.  

When I got my first stick shift, I went to San Francisco. SF has a to of hills. It was baptism by fire. I smelled some burning. 

But my next trip up, I got the hang of it. No burning smell. It takes practice. 

TBH, I didn’t really look at the RPM, I just did it by feel. Making sure the car didn’t stall. 

When you smell the clutch burning you know you're slipping it too much. If it's that much trouble and you need to do a lot of uphill starts you might want to buy a Studebaker with the "hill holder" feature.