A sign specialist does just that, specializes in signs. Whether you go to a sign specialist to get a custom layout for your sign or banner you will be receiving the benefit of the sign specialist expertise.
When you order your signs or any of the other products that are available from your online sign website, you are also getting their expertise, their equipment and their printing techniques. Some of the sign shops may specialize in large format printing. Some can print almost anything that is sign, banner or vinyl banner, billboard or magnetic sign related.
You used to have to visit a sign specialist at a printing shop to get these items but today, you can get them instantly online. After you have ordered them you may get them delivered to your door very quickly.
These companies are in the sign business to make money and that means providing you with outstanding customer service. You can do your own layouts or get their expertise and assistance in the lay out and design. They can assist you with font choices and even using your own artwork versus their own usually extensive clip art file.
Since you are spending the money for advertising you should make sure the resulting product is as visually interesting as you can make it. It also needs to say what you want it to say in as few words and graphics as possible. Not everyone is an art designer but a sign specialist has seen a lot of artwork so they have a very good idea as what will be effective or not. Since your experience is running your own business a sign company is in the business of making signs, so take advantage of that experience.
And consider using other forms of advertising like a 3' by 10' vinyl big banner in vibrant red with bright white letters or a billboard banner that is bold and in your face. As the vehicle speeds by they have the visual impact of right now. Several placed alongside the highway will reinforce the message. The same sign company can assist with these also.