Recently i have transmitted my practices and turned to do more of a full body breathing awareness and find that it actually stablizes my concentration even sharper than fixation on the nose. If one wills, one can contemplate the characterisitics of the body while using the breath as an anchor and still find that one becomes sort of absorped into the process of breathing then one can go back and enter the nostrils with awareness. Choosing to stick with the full body method, i find that the calming of the bodily fabrications comes naturally and that one can certiantly calm the intention. However, as Thanissaro teaches, one can if one wills, to simply change the pattern of breathing and simply expirement with the feelings they induce or act upon.
Honestly, both methods are reliable ways to enter jhana as far as i see it.
May your practice go well to all
With metta, mike