How can a mountain biker effectively transition from an aggressive trail braking style to a more controlled and precise technique suitable for technical, slow-speed descents, considering factors such as varying trail surfaces, tight switchbacks, and unpredictable obstacles, while avoiding the pitfalls of over-reliance on the rear brake and maintaining optimal body positioning, especially when dealing with steep, rock-strewn or root-infested sections, where a moments hesitation or miscalculation can have disastrous consequences - and what specific drills or exercises can be done to develop the necessary braking skills and muscle memory to navigate these challenging terrain features with confidence and precision, all while leaving the hapless roadies in the dust, of course?