So you want to start start building kits? There is a lot skills you will need especially if you have never done any car modeling and fiberglassing. The approach is almost the same regardless which kits you will be building. Right from the beginning you have to make a decision if your going to build just a few cars or more as this will dictate how much detail you must put in to the PLUG (the full scale model of the car).
I guess the plug is the most crucial part of building kits since this is what you will be pulling the mould imprint from. If you don’t pay careful attention to the details in the plug all the imperfections will be transferred to the mould then to the final fiberglass kit.
Another big mistake builders make is not stiffening up the mould during the creation process. Usually you can add more stiffness glassing in some hard materials over the top of the mould. Wood, steel, pvc piping and even rolled up newspaper can be used for these materials. This is a industry standard trick it stops the mould from warping and reduces the number of layers you need for the mould.