Found this cool pic of the battle, made about 100-150 years after the battle, but still a nice visual reference.
I finished cutting figures from sprues and trimming flash yesterday. The Red Box orcs I'd ordered a while back were nice molds with very little flash, but the Koreans had quite a bit, and the Japanese Ashigaru spearmen were making me play Queen's "Flash! Ah-ah!" in my mental music player as I trimmed them. Luckily the Ashigaru archers/arquebusiers had very little on them.
I need to pick up some paints to add a bit of color to easily distinguish units and troop types (no time to give them good detailed paint jobs). Koreans will have light and heavy foot in equal numbers (48 figs each), while the Japanese will have 100 light foot--the ashigaru--and a mixture of heavy and armored foot from my Zvezda samurai infantry (44 figures) and the medium cavalry (17 figures).
I may give the Korean defenders a cannon or two, as they did historically use cannon for defending fortifications (no idea if there were any at Dongnae during the battle--likely not), and they may need the help it will give them.
Then I just need to print up and laminate some terrain feature cards and walls, slap together my model of a fortified gate, and I'm ready to rock this game.