In essence, what Manfred describes is the process that Lightroom can automate for you. If you select the eyedropper tool from the white balance panel, place it where you want in the image, and click, it balances RGB values at that point. This is one of the reasons I like starting in Lightroom, particularly when I have a series that needs the identical adjustment of white balance (e.g., a stack of images for focus stacking). You place the eyedropper over the whiBal card (or whatever you are using) in the first image, click once to adjust white balance, and then tell LR to sync that setting over the rest of the series (which have no whiBal in them). Alternatively, you can adjust to taste before syncing. It's about as easy and fast as it possibly can be.
Capture One has the same functionality. What I find is that it can give a good starting point, but I will tweak the individual colour channels as that tends to give me better results if I don't happen to have a gray card or white card in the shot. Often I find that I don't want a completely neutral shot and a tiny bit of warmth or coolness works better for the image than going strictly neutral.
Exactly. That's what I meant by adjusting to taste, which in my case almost always moving slightly warmer. However, I find it very helpful to have a neutral starting point, as I find that I often don't find that neutral point on my own when I start a session. I often start too warm if I don't have a neutral source. In fact, I find that I sometimes drift during an editing session and need to compare earlier images to recalibrate myself.
I haven't done much editing since having my cataracts removed recently, and I am curious to see how that affects things. I'm 5 weeks out for one eye and 7 for the other, but I still sometimes find myself thinking that the world looks a bit blue and that grays and whites have a touch of magenta. In other words, my brain hasn't fully undone its having gotten used to the slightly greenish yellow cast of cataracts. So I expect to rely even more on my whiBal for a few months.
Dan - I agree with you to an extent, as I use a similar process when I include a neutral sample in the shot.
On the other hand, I also suggest people use the sampler tool to get a reading to understand what is happening in the scene. In my view unless the photographer understands how colour works (the primary colours and their compliments) and how to adjust for colour issues their approach will be a bit hit and miss.