I try to do my best, but miss it sometimes. Thanks though.

You are right, trial and error is best, and the test for Silver retention is a kit which has Sodium Sulfide in it. It turns yellow, brown or black depending on the level of retained silver.

However, I point you to a thread with the subject the yellowing of prints. This person was using the Ilford method, but had prints that turned yellow quite rapidly. This was also experienced by Ctein who wrote an article on it. You see, water varies world wide, photoproducts vary in thickness and silver level and etc. Therefore it is hard to predict.

In the US we use Chlorine to treat water, but in other parts of the world, they use Ozone for purification. This greatly complicates the situation.

You should run your own quality assurance tests, and be aware that overwashing is as bad as underwashing.