what about starting off on a hill with a person up your ass
the act of a hillstart is simply to allow the drive wheels of the car to be supported by the engine (rather than the brake), so when you take off the hand brake, instead of rolling back, the car remains where it is, allowing you to then move the car forwards.
hill starts are complicated; you have to hold the clutch at the biting point and push the brake down and then release the brake and the clutch slowly, then accelerate after lifting off the brake
i'm not sure if you've attempted a hill start but this is the best way to rollback into the car behind you.
first off, due to humans only having 2 legs, you don't want to be using the brake pedal at all, and be using the hand brake instead. this allows you to use the gas pedal and clutch pedal at the same time. provided the car is in gear, at this point you rev up the engine, release the clutch until you can feel the front wheels begin to pull (the car will move slightly as the wheels begin to support it's weight). now you release the hand brake and the car will start to creep forwards. at this point you can release the clutch further and provide more gas to move away faster. once you get good at this stuff you can ride the clutch and not use the hand brake at all.
if you have the ability to move the car without providing gas whatsoever (just using the clutch), you probably have some 2litre petrol thing or a diesel engine. most ordinary cars have to have their clutch and throttle combined together, otherwise they stall. also, modern cars have all sorts of fancy bullstuff like anti rollback (aka a hillholder), which means the car remains stationary on a hill even when the handbrake isn't activated. i would never trust this.