Looking at one's fingernails at Havdalah

Hi, When one recites Havdalah ending Shabbat, one recites a berachah before a flame and looks at one's fingernails. There is some debate regarding the nature of this berachah: Is it a berachah praising Gd (birkat hashevach) for giving us light, and so one could use the flame by looking at his nails before reciting the berachah? Or is it a berachah thanking Gd (birkat hanehenin) for the benefits of His life, such that one should recite the berachah before using the flame's light? Our practice is to recite the berachah, and then use the light. (Rav Moshe Feinstein, Igrot Moshe Orach Chaim 5:9:9) Have a great day, Mordechai