I've got an EM 10 also, I used to use it like that too. Now I use a beseler pm2 analyzer pretty much the same way for B&W printing. I can get twice the range on it as I do the EM 10. Stll takes a while to get things zeroed. Usually when I get a good tonality print I'll do some readings on selected areas and jot down the results along with the time and filtration. Pretty soon I have a list of values for each time and contrast filter setting I use the most and saves time and paper. So if I make a big print and my aperture is nowhere big enough for a 20 second reading I can shift to a 60 second reading for similar tones and get on with business.
As and alternative you can do your setups for a standard aperture setting and read your values to find differing times for each tonal value. I think this takes longer to establish but can be worthwhile.