You can forge a blade with a rock if you want to, I just showed the hammer in that other thread and said I like them and who I got the idea from.
It's better to understand the basic physics behind moving hot steel than it is to have a bunch of fancy hammers. Once you understand the type of stuff I was poorly trying to explain about steel movement, you can accomplish it in all sorts of ways.
Many guys with experience could do all that same type of movement using just a single hammer... by varying the angles and by adjusting just how much of the hammer face, or corners of the face, they use.
I have a video of Bill Moran forging a big bowie very close to shape with nothing but an ugly, old, beat-up ~3 lb. cross pein with a fairly round face.
If somewhere along the lines I started telling everyone the way I do things is the only way and the tools I use are the only way to go, then I guess I don't remember that.