Questions on helmet detailing


Jr Member
I see some pics of helmets where they are using more peices of card stock to make the helmet look fuller, how does that work?
Even though Bondo is explained im not sure how to use it and dont want to mess it up. ( this is vaguw so ill just try this one i guess)...

If you want to do an indented detail like a small gap making it look like two connecting pieces, do you have to bondo that whole peice to get that look or just those edges and sand them to fade to flush?

Would love any help on this, if i just try it ill probably figure it out sooner or later, but with the wealth of knowledge about this on this forum id thought id ask here first before i ended up wasting a whole lot of money, and time.