MDR can be surprisingly accurate generally over short distances of, say, less than an hour. For long flights the traditional whizz wheel may be better but really these only occur after training when more sophisticated planning tools can be quicker and more accurate.
I was given a program at Finningley which could resolve the navigational computations very quickly. I modified it to include all the standard routes. Selecting a given route, inputting wind, and bingo a flt pln that took only as long as it took to copy the numbers including fuel.
I then modified it again so that I could enter a student's data, including errors, to confirm that subsequent calculations were correct even if based on incorrect data. I could analyse a sortie in short order and give a same-day debrief.