Hi, so I have this mould that will be used just one time and theb scrapped.
It is made with epoxy gelcoat and a few layers of 200gsm cloth laminated with epoxy.
I want to infuse the part and I think the mould is too flexible for the job.
What do you suggest as the cheapest way to stiffen it?
I was thinking about breather cloth impregnated with cheap polyester resin but maybe you have better and cheaper ideas?

Thanks for any advice!

Breather cloth with polyester will not work at all: there are not fibres, that would make the mould any stiffer, the polyester resin will shrink a lot and warp the mould, and polyester resin does not stick to epoxy to begin with.

The cheapest way are some eps foam strips and 1-2 layers of any glass cloth you've got laminated with epoxy.