The manufacturer is generally quite willing to sign a document protecting the proprietary nature of the innovation and is, depending on how busy they are, glad for the extra work. Engineering of the product and the preparation of prints from which manufacture may proceed is a service also available from this office. The hard part often is marketing. Companies try very hard not to make things which can't be sold at a profit for very good reason. Obtaining distribution can be difficult.
Conventional advertising is expensive.
The Internet may provide an appropriate and inexpensive answer to this problem. The most important factor, however, is persistence. Lack of knowledge, experience, and expertise are all relatively unimportant if one is willing to learn and persist. An example of a successful inventor who knew virtually nothing of patents, engineering, manufacturing, marketing or any other aspect involved in making a success of an invention, who has done all of it on their own with only the professional assistance of those required for such tasks as acquiring the patent, prototyping, and manufacture is Mr. Paul Swisher. His invention, an attachment to a fishing rod, which provides a handle above the center of gravity of a rod and reel and which relieves strain upon the wrist caused by bending the same to grasp the rod, is pictured below.