YiffieMon:Skill Defaults
You have to make a skill check of the Defaultee skill with the same DL to use the Default from that skill on a skill you don't know.
Hplus of the skills default values it the BOK to train it.
If you fail a knowledge check with a skill you can retry with a default value that skill.
If you But Success a skill check you can reroll using one of the skills Default value that hasn't already been use on this roll, just reroll, you don't need to make a skill check in the Defaultee skill.
Defaults and experience
when you gain Experience in a defaultee skill, make a skill check of the defaulter skill with a DL of the amount of Expertise Points earned; if it fails you get that amount of ExP to Defaulter skill and repeat the process on the skill(if the defaults graph is not a tree you have to check to make sure it's not gaining the ExP from multiply paths)
defaulter skill = the skill that defaults to another skill
defaultee skill = the skill that the defaulter defaults to.