For the Newport News battle, form three infantry brigades to make up the entirety of your first division before the battle. You will start with these three brigades, plus a small carbine-cavalry unit near the top of the map. You will get substantial reinforcements from the SW after 1 hour, and then a supply and cav unit from the SE after another hour.
At the outset of the battle, bring your starting brigades immediately south into the town and use the cover of the town to defend. Dismount your cav unit in the town and use it as an infantry unit. When reinforcements arrive from the SW road after 1 hour (which will be just as the Union attack starts) rush them into the town and just to the NW of the town to strengthen your defenses.
The Union ultimately will outnumber your force about 3 to 2.
Your defense line should run from W of the town along the stream across the top of the town and down the E side of the town. Use cover, especially the buildings in the town, and use skirmishers to flank Union brigades.
It is especially important to keep the Union brigades off the W side of the town—it’s also not hard. Due to a bug presumably, the Union troops tend to become stuck in a “rout” state while in the stream near the town, and you can shatter them over time from the cover of the town buildings without taking many casualties. The attack from the E you can repulse with the help of flanking units from the south.
This is not a difficult battle, even though you are outnumbered. You should take out half or more of the Union force.
When spending Career Points after a battle, bear in mind that you should have an Army Organization level of 6 by Shiloh, and 9 by Second Bull Run.
The basic strategy for this battle I have outlined above also works when using the J&P Rebalance Mod.