I don't know if there is a guide but i found this:
What is the elastic effect? it’s described as “The increased or decreased speed a skill will train at when its corresponding skills are higher or lower relative to the said skill.” What this means is that in order to effectively train a player, you’re going to want to rotate what skill is trained quite frequently. An example of the elastic effect would be when a guard with all respectable skills is given non-stop jump shot training. Each new jump shot pop is going to take longer than the last because of all the respectable skills slowing it down. Alternatively, if you had a guard with atrocious jump shot (and all his other skills at respectable), his jump shot would increase at a faster rate than his other skills. BB players have a natural tendency to strive for a balanced game so do them a favor and mix up your training every once in a while. The more you rotate training skills, the faster a player will train.