brendo are you using a laminating resin with hardener ?
watch out for that MEPK, it will burn your eyes etc if you get it on your fingers then wipe your face.
i use a UV cure Resin, you lay it on in the shade or inside, then when you are ready to dry it,.
you just put it in the sun, in 5 mins it is starting to set, an hour or so and it's hard.
it is good stuff as you don't have to worry about it going off in 5-10 mins
how long are you leaving it to cure once you have laid up the mould, and are you bracing it with wood/ alloy to hold the shape
it will need to be 5 or 6 layers layers thick if you want it to last too.