I to have always used DB's recommendation, plus a calculator. The combined system might be known as the "floating hundreds" one, and was taught to me by a Nav (they used to do numbers). Enter each time with an extra "0" between the hours and minutes, i.e. 1hr 32mins enters as 1032. Thus:
1hr32mins+5hr17min+7hr21min+13hr37min+2hr19min+14hr05mins becomes
1032+5017+7021+13037+2019+14005=42131.
i.e. 42hr+131mins=42hr+2hr11mins=44hr11min.
It is easier than my clumsy explanation makes it appear, and means only one minutes to hour conversion per calculation is required. Obviously it doesn't work beyond 999mins, but has always sufficed in doing page summaries in the log book (seven in my case as well).