Slightly aside but I believe relevent
when balancing interneg material, we would use three distinct methods of balancing .
1 curve plotting method(least reliable)
2. density difference (very reliable)
3. computer software plotting method(very reliable)
in all cases before we used the paticular batch of emulsion (we would purchase 1000sheets at a time) we would expose a graduated grey background that was lit from white to dark with even spread.
we would print this negative and balance for grey and then look at the print and *eyeball * the area where a cross curve would be evident and make a final correction based on a visual rather than what the charts said.
For colour negative printing the best method that I used was the VCNA method. where one balanced in a standard well exposed shirley to print , then video analysed each film and image to this standard.
A manual method I use daily now is to take a very nuetral image with the six main colour groups evident ( cyan, red, blue , yellow, green and magenta) as well as black white, flesh tone and a good grey. I then make a colour ring around based on what I and others here think a good print balance is . This ring around is then put in the colour correction lights and any new test done is compared to one of the biased prints and a print correction is made from this. (this method usually takes no more than 3 test usually less to be in balance )
I agree that finding density first is a good method before colour balance, if you do a density ring around on a good colour print you will find that a light print is biased towards cyan and a dark print is biased to red. This bias can throw a wrench into things when colour printing.
All digital printing devices to RA4 material now use a 21 step grey scale for balancing out to nuetral each step before printing is allowed.
Personally I think the Colour Ring Around approach is the best and most accurate method available, because you are looking at what off colour prints look like compared to a standard that is balance properly. Your eye gets trained to judge good colour and also to see the imbalanced mixtures of colour
After using this method ,combined with colour theory I have never seen an operator not improving within three or four sessions.(unless of course they are colour blind and then the mathematics should take over.)