Yep, PVA is your friend. Spray it on like it's a paint, get a nice thick application. You won't have any issues. If the paint is a really bad job then it may come off the part and stay in the mould, but as long as you've got PVA it'll come off with a quick blast with a high pressure washer. 

Thanks again for the replies.

Personally I don't think it's an issue. Spray PVA as a release agent and there will be very minimal sanding needed to make the moulds glossy. Quick flat with 1200 then compound would do it. 

You will have problems in that you have to remove the sponsor vinyl stickers as they will come off when you gel coat, its reactive enough to fetch paint off so you need to work this into your build time.

Thanks for that.

I thought the best solution would be to paint them, but it is going to take me a while to get it all done and the car will be in use during this time, so i didnt want to be running around with a patchwork car, plus i have to run sponsors stickers.

I guess i shouldn't be trying to do everything at once and risk compromising my mould

you can certainly take a mould off the surface, but you will need to wax and release it like any normal part and then spend the time sanding and polishing your mould to get the desired surface finish.

Hi folks.

i have a car which a previous owner painted matt black, its not my choice, but it is a race car so spending a lot having it resprayed is a waste as it won't make it go any faster!

i want to mould the panels as spares, but in carbon, and hopefully replace all the panels with home-made carbon ones eventually, but can i take moulds from something that is painted with a matt paint or will it adversely affect the surface of the mould and will it tend to have more bite- so it won't release cleanly?

thanks