I’ve been making multigrain breads for nearly 50 years. The first time I used cornmeal it came out quite dry. I know how much liquid corn absorbs when it cooks, so I decided to try pre-cooking it. I simply add the grain mixture to boiling water and turn it off immediately, let it cool for an hour or so and then add yeast and revert to the previous case. It works.
My recipe:
1/2 cup each of corn meal, oatmeal, ground flax seed, skim milk powder and a heaping tsp. salt into 2 1/2 c. boiling water. Decant into a bowl and let cool an hour. A half cup water, a half tsp. each of sugar dried yeast on top of the cooked mix and allowed to prove for 15 minutes. Then I mix in to the cooked grains about 3 cups (I don’t measure, so this is a guess) of flour, half whole wheat and knead a dough and let it rise overnight (else use a full tsp of yeast and leave it a couple hours) in a covered bowl. Knock it down shape it into a buttered bread pan and let it rise for an hour or two and bake it 50 minutes at 425.