You are definitely on the right path. When I post-process a recording I always take notes on the avg RMS levels and the peak levels. I write that down in a notebook, and it also includes my location in the venue, mic pattern, the gear I ran and the gain I ran. That information is absolutely invaluable for estimating the required amount of gain, pattern choice, etc, at future performances.
There is a really great
free command line tool, called normalize. I
love that tool, and I've been using it for over a dozen years. It will report levels, and set levels based on peak, or avg RMS. It can just increase gain, or it can do compression to raise the avg RMS while avoiding clipping (that is the default). It can treat multiple tracks independently, or it can scan and adjust all of them so they are uniform (batch mode).
You can have it add a fixed amount of gain to files, you can have it just apply a limiter, etc. It is very powerful.
To scan some files and just report the levels:
% normalize -n *wav
Computing levels...
level peak gain
-33.7506dBFS -4.0635dBFS 21.7506dB w1.wav
In that example, file w1.wav is just a random file. -33dBFS is the avg RMS level (that's really low). It peaks at -4dBFS. The default behavior of normalize is the adjust and compress as necessary so the avg RMS is -12dB. That is pretty hot. So if I ran it with default settings, it would increase the gain by 21.75dB, but it would first compress the audio to prevent clipping.
I don't normally compress my audio in this way. But an exception is when I use this tool to quickly take a recording, with individual tracks, and make a "car" version that is louder for windows-down driving, etc.
Normalize
This is release 0.7.7 of Normalize, an audio file volume normalizer.
You can get it from here:
http://normalize.nongnu.org/