Casting/Molding Sergeant Helmet Skulls w/ GS

[Alcyon]

It drives me crazy when GW doesn't give you all the optional bits you need to comply with the Codex Astartes! Specifically I'm talking about every single kit from the Start Collecting Vanguard box. There isn't a single skull-logo sergeant helmet in the box, just a ton of bare heads - and don't get me started on the Phobos Lieutenant, who's armed (and visored) like an Incursor, but has a grav-chute and no Omni-scanner rule.

 

Accordingly I'm wondering if anyone has tried making those tiny skulls, either by casting them from another helm or by modelling them by hand. I'd love to add one to a Suppressor and a couple of Infiltrator helms. I took a look in the search and Tutorial thread (and google) but no dice, except that I seem to recall someone working on these years ago when I was into the hobby before. Anybody have a tutorial link bookmarked or experience working with very small pieces like this?

[Jukkiz]

you could make mold pen out of variety of molding tools, one end to have skull imprint and one to hold from it.

Fill the imprint with something like greenstuff or variants and just make all the tiny skulls you need