The good news is there is no “correct” way of valuing the shares. The bad news is there is no “correct” way of valuing the shares! In my experience it’s just a case of taking an intelligent position and then fully justify that position by explaining the method you’ve used and systematically showing why/how you’ve ruled out any other potential methods.
There is a growing realisation amongst valuers that there is no such thing as a “financial control premium”. The only benefit of control is the hypothetical (and able to be substantiated) forecast improvement to the shareholder’s position if they happened to have control, as opposed to not having control. But control in isolation itself isn’t worth anything. This gets into the “strategic benefits” territory where the shareholder might have say another business and he wants to force this business to supply to his other business at a lower cost so that the other business makes more money. If you could quantify the increased value of the other business you could almost draw the conclusion that this particular shareholder might pay above the intrinsic “financial value” of the business because of these external factors. But because the external factors are different for every potential shareholder it is hard to predict and substantiate if there is a strategic benefit for any particular class of shares and if so, how much. This is all very hypothetical and so can probably be justifiably ruled out by the valuer in many cases if it is well articulated in the valuation report.
Would you buy a term deposit if the interest rate was 0% just so you can say you are an investor in the bank? But what if it meant they gave you a discount on your next home loan because you were a depositor? That is the starting point for these types of arguments as I see it.
There are no formulas for these types of things, so you need to think long and hard about what the real benefits are in each specific case.