Honest advice? Hire someone to do it. There are so many things that you won't know about how to make things manufacture-able it would be worth your time and money to just pay a contractor/employee to optimize things for you.
(shameless plug, my username @ gmail.com if you would like to discuss what services I can offer you)
If you want to go that route, have a contractor review at various stages. It shouldn't take more than an hour or two, and most contractors will do it with the hope that if you make it big you will remember them and their services.
(shameless plug, my username @ gmail.com if you would like to discuss what services I can offer you)