What is the technique?

that simply mean you're overweight.

I vomited lasagne all over my bike when I was over 16 stones after trying to cycle up a very steep hill in the mist of Surrey.

now I can attack hill without too much problem after getting rid of the excessive 4 stones.

Err.. not exactly. You can be 55kg, smash it over a hill and puke.
It depends on the effort you put in. If you're 150kg but have inverse shimmed gearing you could climb loads of steep hills without too much trouble - it'd just take all day.