This exploit working only on L2j Custom servers (such as aeL2, L2 Insanity) with sublasses on. With this exploit you can learn ALL skills of other classes on one char. Maybe many ppl know this exploit, but I think that not all ;)
1. If you already have a subclass, cancel it and change to one which skills you want to have.
2. Now go to Master, and click Learn Skills but don't learn them and leave this window open.
3. Go to Grand Master and change class to your main.
4. Now go back to the master and Learn Skills from window that you haven't closed ;)
Sometimes, at the begining you can't learn skill... You just have to learn one skill which works and then you can learn the others. Heal, Group Heal and Battel Heal always work for me, so learn them first and then learn others.
Sry, if you can't understand something. English isn't my native language.