Fisherman hit it bang on,
Epoxies and polyester resins are two totally different animals to mix and use.
Another thing, working with epoxies or polyesters isnt the easiest when it comes to hot days like today, your working time will be reduced drastically, make sure you do it in the shade as if your using glass it will bubble on you if in the direct sunlight. Cooler days would be better.
The cure is a chemical cure so air does not affect curing, its all temperature related, so the only thing air flow is good for is ventilation.
You should be able to find out the pot life of the material which is your working time if it is epoxy. If your using fiberglass resin use close to the reccomended amount of catalyst, you can cut back on the catalyst but cutting back on the catalyst too much may leave you with problems as it may not cure propely and be soft.
A trial run is always a good thing.