BTW, if you're using R80.10 and above, you can do something really nice with layers.
If you create an ordered layer and place it at the end (bottom), then all traffic that passes the previous layers will go through it as well. In order to be accepted, traffic must be accepted by all layers, so put a cleanup rule for Any-Any-Accept, Track=None. This will ensure that the layer doesn't change the traffic handling.
Now you can add rules above the cleanup for the specific traffic you want to log with accounting. For example: Source=my_network, Destination=dest_network,Accept, Track=Log+Accounting.
Any traffic between that source and destination will add accounting information to the logs. This way you don't need to "hunt down" the relevant rules in your big policy. Also, if you only need accounting on some sub network (that is smaller than the scope of the rule), then this way the accounting will be added more granularly.
You can also use this method to add Detailed or Extended logging on certain traffic. You can even add Alerts on certain suspicious traffic that you aren't sure you want to block.