I'm currently working on a Jango Fett Scratch build for my son. After finishing Boba at a 92% scale for my older son, the younger was perturbed (rightly so) about not also having his own awesome mando helmet, so I decided to make him Jango (because I'm crazy and hate my free time).
I started with Rafalfett's v1 templates, foamcore, sintra, cheap bondo fiberglass resin, and an el cheapo silicone caulk mold I made for the dome portion.
By the way this guy has a pretty good tut on making the mold. ...and says "actually"... a LOT. https://youtu.be/tBClhbrGR7w
It's a cheap way around dropping a bunch of money for making a 1 off mold...I can't say I'd do it again though. I managed to make it work, but I got no where near the results this guy did in his videos.
I have 2 layers of fiberglass in the dome...it will take a basball bat I'm pretty sure.
...and where I am currently.
I had to modify the key-slot configuration to match the Jango with a little more spacing....and the back-bottom portion of the outer-cheeks had to be widened a little. The dark stuff inside the helmet is Bondo Glass, which is thick resin premixed with fibers. I use it to give extra support to the stress points before I lay the inner fiberglass. I also JB-welded my T-nuts in beforehand so I could use the bondo glass to help reinforce them.