My exposure time (when using the Opemus 6a) is 10 seconds. I use an Ilford print exposure meter, and adjust filtration for contrast, then set aperture and ND filtration to give an exposure of 10 seconds. If the contrast isn't right, I then decide whether to change the filtration or try burning first.
I have ended up never dodging, but I might well burn in everything but one tiny spot...

My timer is a metronome - if it was good enough for Saint Ansel in the Dark, it's good enough for me!