These guys are really helpful and quite a bit cheaper than buying fibreglass from the large supply chains such as Bunnings / Supercheap etc.
Basically you need three things.
You mix the Resin with 1.5% of Catalyst apply to the Matting wait for it to harden, and then PRESTO you have a mould. You can then apply as many layers as you see fit. Depending on the matting normally 2-3 layers should be strong enough. It's better to work under conditions of about 22 degrees C just to ensure that you get the gel doesn't dry too quickly or not dry at all.
The good thing about fiberglass is that it's extremely light when finished, albeit messy to work with.