You need the maps and the rules. You can use the rules or Blacalc to calculate the resources a nation may spend. Then you can use the Blacalc to check how much the nation spent on the map. Then you can change its production, zones, etc. It gets tricky in late game and in big wars, because you have to check how much other players lose too, and there is no easy method for that.
But when I check resources etc, I only use the rules and Blacalc.
Fiah: You're not stupid if you can't check it. It can get really, really hard in a late game war... In game three the results often ended up being a bit off when I checked the map every once in a while... Errors accumulate over many turns. It wasn't because I was trying to cheat, but it's really hard not to make just one mistake when checking a big map with many things to take into account. Usually it's not because I can't remember the rules, but the biggest problem is remembering how many of each thing were built/claimed/conquered from each player after and while counting them. I put them into GIMP and use a "difference" filter at high opacity to make it more clear or quickly swap back and forth between two map images of succeding turns.
I'd volunteer to be game manager. I'm not sure if it meant I couldn't play, though.