In Feynman's 'Surely You're Joking, Mr. Feynman!' there is a chapter where he describes his observations on 'how does it feels to go to sleep' as part of an essay for a class. This and other lectures/writings from Feynman gives cues to his technique and also the almost impish curiosity with which he approaches a problem. IMHO the best way to master or learn from him, is read/watch his works/lectures.