The secret to a good tit-fucking climax is that you don't use your hands or cheat by sucking the head of the penis as it slides up and down between your breasts. It's all about good boob-squeezing technique and the right amount of lubrication in/on your cleavage. It's really important to provide that tight pussy-like feel. If done right no manual or oral stimulation should be necessary (unless requested of course).