Lighting Strike will, however, take you all the way to 120 if you prefer. Then use Lightning Strike on your opponents until you reach a real skill of 50 remove your jewelry and continue to use Lightning Strike until you reach 110. The best training method I've found is to train the skill up from an NPC and use jewelry to get yourself to 50. Do not accept the quest until after you have bought your skill you cannot buy skill while on an accelerated gain skill quest.
The NPC trainer for bushido in Haven will train your skill up to 40, and you can train with accelerated skill gain in Old Haven if you accept his quest. The Bushido required to successfully cast each ability 50% of the time is presented on the Formulas and Game Mechanics page. You cannot train Bushido from below 25 skill.
Note: If you are on a murderer, you will have to use a Soulstone or get some jewelry to raise your skill to 25. With it and the Book of Bushido (purchased from Tokuno Islands scribe NPCs or looted from Ronin), the Samurai can perform a variety of special abilities that mostly are defensive in nature - but can be used to quickly and honorably defeat the toughest of opponents. Bushido is the main skill of the Samurai, and embodies the very essence of honorable combat.
