Hey TS.
There is no accurate quick and dirty method, but there are several components you should look at.
1. Count - How many units on each side. This is the most important metric generally speaking.
2. Punch - As you mentioned, add up the hits-on values (divide by six for expected hits).
3. Skew - The balance within a force that has lower hits-on values protecting higher hits-on values.
Consider this fight: 10inf 10tnk vs. 20 inf.
Count: oCount = 20, dCount = 20
Punch: oPunch = 40, dPunch = 40
So counts and punches are equal. But the 10inf 10tnk will annhilate the 20inf due to skew (72% win for attacker). Early in combat, the attacker is losing 1’s while the defender is losing 2’s.
Any quick and dirty method that doesn’t take skew into account won’t be accurate.
Some sample battles for you to look at:
The Baltic UK1 - Run the battle with 2ftr 1bmr vs 1tra 2sub 1des. Then add a sub or tra for the Germans and watch what happens. That battle can teach you a lot about tactics (force composition).
Frindo UK1 - Run 3inf 1ftr vs. 2inf 1ftr. Add an inf or two to watch the changes.
Holler if you want more.
Peace