One of the most difficult parts of starting a new business is successfully executing on the idea. Fortunately, you seem to have already figured out the product piece with your prototype and relevant industry experience, which means you’re actually further along with the business plan than you may realize. You've already defined a problem in the market and have created a solution. Still, as you noted, there is more work to do and steps to follow to increase your chances of success.
The next step should be to formally construct a business plan. It doesn't have to be a lengthy 20 plus page Word document. Rather, a slide-deck containing all of the key components of a business plan should be sufficient and may even be more useful. It should be a condensed version of a business plan with all of the key elements in a bulleted format or graphical representation. You should include the company's mission, management team/key roles, market opportunity, value proposition, product detail, distribution strategy, competitive analysis, sources and uses of capital, projected financial model and risk factors. The purpose of the business plan is to provide a road-map for you to follow. It does not need to be perfect, as you’ll constantly be improving upon the plan.
One of the reasons why you need to focus on a business plan first is so you can build a team. Unless you've been working with specific team members who share a common vision for the business, you'll need to be prepared to do some convincing. A business plan can help you formulate your pitch and provide answers to questions that you may not have thought of before.
Distribution is another key area to focus on while you're working on recruiting team members. I recommend you focus on the distribution channels you believe would be most likely to bring your product to market. You shouldn't waste time and energy with the largest distributors, as it’s likely too early and you’ll first need feedback from the market to help improve your product.
Of course, this endeavor will require capital. You'll need to determine whether you'd prefer to seek a traditional bank loan or angel investor or venture capitalist to fund the business. Please note that most venture capitalists will want to see some traction in the product and financial commitments from others before getting their feet wet. It would probably be most efficient to work directly with a bank or angel investor first to get the product to market. Once the product and model is proven, then it will be easier to go after the bigger fish and possibly get a better valuation.
Lastly, be prepared to make some mistakes. Every entrepreneur runs into some problems, even Mark Zuckerberg. It's important to not dwell on any one mistake, but to rather learn from them. This will help you grow as an entrepreneur and company.