OK...here is a part that I am making. Here is the mould. I did it with the EC gelcoat and paste for high temperature, anticipating that I could then use it for hand layup and prepreg. I am making my first part by hand layup (because I need to check all dimensions are good at the end). But man it was a mess with all the shapes...do you guys think that I would really be better with prepreg or would it be just as hard ?
Thanks !

Pre-preg would be easier to achieve a good result. In terms of lay up, you can actually use wet-lay in much the same way as pre-preg by creating what is called a 'wet-preg'. Basically just putting your reinforcement between two layers of plastic, pouring your resin over it, and then using a squeegee to wet out the reinforcement and squeeze out excess resin. Then if you leave the plastic in place, you can cut the reinforcement as accurately as you could a pre-preg, allowing you to use templates to kit out for your mould geometry. If you leave the resin to cure for a little bit, you can choose how tacky you want your material to be for laying into the mould. You can use it wet, or you can let it cure to a b-stage, where it would handle exactly the same as a pre-preg. You can even stick it in the fridge or freezer to slow the cure or keep it for another day. 

In terms of the result you will get using that method, it is still a wet-lay and wont be comparable to a proper pre-preg. But it may make the process much easier for you, allowing you to achieve a better result than you might have with traditional wet-lay methods. Certainly if you have the facilities and equipment to use pre-preg, that is a far superior process and definitely a path worth going down.