I'm using some polystrene cones on a weapon i'm making and was wondering whether a few layers of gesso would do or should i put a few layers of papier mache on first and then gesso to help strengthen it? Any help is appreciated ^_^

So many ways to skin this cat!

The BEST way would be to give it a coating of polyurethane rotocast resin. Though without experience, it could end badly. There's a lot of mess, sanding and general room for huge errors.

Several layers of PVA glue would be my suggestion. eventually the PVA will smooth out things and seal the surface, but drying time might be an issue...

Use Halfords acrylic based car sprays to finish. Don't go near Plastikote and it's ilk, it'll just craze.

Thank you Xaerael I shall deffo be trying the different spray paint and i have loads of PVA glue to give that a go

I can concur with Xae.

I used several layers of PVA glue to seal parts of my Raiden helmet which were made of polystyrene. They sprayed up fine with paint once dry (I used Halfords primer and acrylic spray paint by the way).

Make sure you get enough layers on and cover it completely, any small hole will allow the spray paint in and it will melt the polystyrene.

Thanks for the help guys I'll get myself down to halfords on my next day off work and see what i can find