Helmet dent

How do you do the helmet dent my helmet I'm making is going to be fiberglass and bondo. should i make the dent in the Styrofoam dome or wait till its done and use a tool to make it?
Thanks

Fiberglass and bondo are notoriously hard to make convincing dents and scratches in. You'd probablye be better off making the dent in the original styrofoam cast, than waiting and trying to put the dent in after the fact. I bought a dent-free fiberglass helmet online and had to put my own dent in it. I had to but a hole in the helmet where the dent would be, glue a piece of plastic to patch the hole on the inside, and then smooth the depression with spackle. all in all, it wasn't that hard, but it'd probably save you ALOT of time to make the dent in the original cast.
my 2 cents worth

Thank you for that