welcome to the forum. there's much to be learned here. there are many from which to learn your chosen art. check the thread for beginners, and while yer at it, lots of info in the tips section.good luck & let us all know how you do.
They don't have to be very special. High speed like mo-max will work fine. Buy round blanks and put them in a steel handle. Bill Hiesman did a video on it several yrs ago, pretty sure you can find it on the web,maybe U-tube.He even made his own hammers. Most are ground like a flat graver But an onglette geometry comes in handy when cutting such large cavities.
There is more people here that can help get you going too.