Jeff,
Making a mould of a hydro is the hardest ones to do, but not impossible. I wont get into too much detail, but will give you steps to follow along the way. If anything becomes unclear then I will do the drawing thing.....
First step: finish the plug (Plug is the shape you wish to mould). sand and prime, sand again with smaller grit paper and prime, until all pinhole have been filled. There are different ways for getting the surface of the plug right. I generally remember that the more glossy the surface of the plug, the same will be for the mould. Save doing work on the moulds to get the shine. Get a shiny surface if you plan to not paint the hull and deck after they come out of the mould, if you want to paint then dont worry too much about the surface of the plug or moulds. You cant have shine if mould dull......enough of that.
Get some good mould release wax and cheesecloth or soft cotton fabric for wax on, wax off, daniel son
You need to follow the manufactures instructions, some say apply wax in small area then buff with clean rag, dont do it in the sun or on hot days. Leave about 15 min between coats to allow the previous coat to set hard. Apply around 8 to 10 coats of wax. It may seem alot but helps to minimize sticking.
Next: Put a flange around the entire outer edge of the plug to form a flange, for when the moulds are together the flanges help position the both halves.
You still have lots to do but that will get you going. Let me know when you want more !!!!!!!