The problem with spraying gelcoat is that it's designed to go into a mould and so the exposed surface stays sticky so to help apply future coats (i.e. the glassfibre).
You can get around this by getting your supplier to put a waxing agent.
For spraying, you'll normally need to thin the gelcoat slightly.
International Perfection two pot paint does the same job and is far easier to work with, though.