Mixing: How To Use Pre And Post Volume

when I try to mix my songs I’m always confused between changing the pre or the post volume. I think I understood that the pre is to choose how much of the original signal to pass. But maybe I’m wrong. The post is a gain.
So, when I start adding tracks and instruments to my song, which volume shall I start lowering?

And for a more Renoise specific doubt: is there a difference in changin volume from the volume column, from the automation and so on? Is there a priority order between them?

The Pre volume fader is for setting the gain into the device chain (although changing the instrument volume setting has more headroom). For instance you might want to increase or lower the volume into a distortion unit to get the sound you want. But as you can also use Gainers anywhere in the device chain it has even more limited value. The Pre volume fader is normally set once and forget.

The Post volume fader is what you would normally use in other software and hardware mixers but in Renoise it has limited value as due to the mixer routing as it is post send. So if you have say a send device to a reverb on the track and move the Post fader down the reverb will still keep sounding at the same volume.

So the best option is to use a Gainer device to adjust volume levels. If you add it before any send devices it will act like a normal Post volume fader.

So the post and pre are almost not useful…

And mixing with gainers/sends is making me tired a lot (hard to see the global thing)

Just bumping this one.
Is there any reason why we cannot put a send device AFTER the post volume device?

This has been discussed like million times here. I’ll tell you: yes, there is. The reason is that it is not made to work that way. And it’s prolly not gonna change.

Here is a discussion on topic.

Well they seem pretty useful to me. You can replace the pre-volume with a gainer, but why use up the extra horizontal slot when there is a fully-automateable volume there already? The post-volume is useful when you already have compressors/distortion or other effects that change the volume in the device chain, and you want to control the level of the final result.

Just consider them like built-in gainers already placed there for your convenience (which I guess is all a volume slider actually is).