I use a microwave as well, for slightly different reasons.
Typically I have a wet dough that has spent one or two days in the fridge.
It happens to be from a sourdough starter, but that's not important.
After taking the bread out of the fridge, it's time for it to rise and be
baked as a boule later that day. I found that the crumb was very uneven
because the top of the loaf warmed up sooner than the bottom. It rose
unevenly and took a long time.
So what I have been doing for quite a while is to take the cold dough out
of the container and onto a plastic cutting board. I stretch it to help
develop the gluten and put the whole thing into the microwave. Zap on high
for seven seconds. That's a somewhat arbitrary number, but I'm trying to
warm it a little without cooking any yeasts to death. Then out of the oven
and back to the counter where I fold the dough over (with wet hands) and
stretch it in the other direction. While stretched out, back it goes into
the oven for another seven seconds. Then fold, stretch, repeat. I keep
doing this, perhaps for a total of about seven or eight times, until the
dough feels slightly warm to the touch.
Because of the stretching and folding, the dough is uniformly warm.
Then into my parchment paper-Iined bowl to rise. Covered with a Japanese
tenugui (because I have one), I place it on a warm shelf above the
refrigerator.
The dough rises fairly quickly. Meanwhile, I have started the oven with a
Dutch oven inside, ready to receive the dough for the Jim Lahey method of
baking.
Transferring the dough into the pot with the parchment paper is easy. The
combination of a wet dough, the warming and the stretching produce a very
nice and very uniform crumb, even with a high proportion of whole grain.
One could also let it rise a bit then do more stretching--it might be
better still.