I am out messing with my paint and wanted to put a built in hood ornament on it.

For subject purpose lets say I need to sculpt it so Bondo goes off to fast. Size? about the size of a palm of a hand.
tried hot glue gun but finish was not what I was hoping for. I used bondo but it went off to fast however the finish was desirable.
I am a carpenter by trade so I am not familiar with metal---yet.
I would like to be able to sculpt it have it dry hard yet give me a couple of hours before it starts to go off or set-up/
For a finish it needs to be able to put up with the rattle and shake of the Vtwin without flying off or ??
I was thinking an acrylic of some kind could maybe get there?

Anyone gotta solution or am I thinking in the future?