Believe me, I would know. The fighting style I use is called "Ryusoken" which utilizes my hands, forming into claws like a dragon. This style was taught to me but none other than Monkey D. Dragon himself.

[He divides his fingers into three parts as described with both his hands, and holds it out to him in a fighting like stance.]

I use it a lot with "Haki" and it's pretty effective against just about any hard material. Be it armor, metal, you name it.