Interesting post and comments -- which leaves me with these questions...
* Do you do the turning & tweaking for the whole song, or just part of it, or?
I run the song all the way through because I want to see what the compressor does dynamically throughout the song sections. But, I'm not learning how to use the compressor. I'm applying compression that I already understand how to use.
* Or is a different approach suggested "for those of us who are still learning" to maybe have a short 30-second song to experiment with? (versus a 4.5 minute whole song)
That's a good way to learn what the knobs do and how they affect the sound. Select part of a song and loop it.
* It seems that I don't get enough time in the studio as is, and I'm wondering if I could perhaps 4X my learning curve -- by experimenting with songs that are 1/4 as long?
Maybe, but time is time, so you need to spend time any way you look at it. Do whatever makes the most sense based on how you learn.
In the end though, you have to listen to what the compressor is doing to your song and spend the time to get it right.
It's important to understand what compression does to a single instrument and also the entire mix. so me sure to experiment with individual instruments and then entire mixes. Personally, I almost never put a compressor across the entire mix; I leave that kind of processing for the Mastering session. But I typically have
very many tracks compressed
individually.
If you really want to have fun, put a compressor on your snare drum. Use the fastest attack and release times it will allow, and crank the gain to hit the compressor really hard. Then slow down the release time and observe the effect. Do the same for the attack time. Experiment with different ratios and attack/release times. I would say that it's nearly impossible to get a good modern snare sound without proper compression. If you master the use of compression it will make a tremendous difference in mix quality and your production with make a giant leap forward.
