Noting I don't cover magnet inserts in these images, it is just a quick and dirty assembly order for a helmet made with large parts. plastic inserts for back fan and lights are also not shown.

Start with a jowl and rear bottom piece

Attach together

next take a temple and top piece, in this case a printed as a single large part

Attach to form a full side

Repeat for other side

Now take the roof and back piece, ( back fan and back bottom printed as one large piece )

Attach to made one long center piece

Add a full side as assembled previously

Then the other side

Add the peak

Now take the three chin pieces

Assemble

Attach to main helmet