Your advertise should contain more information to attract potential buyer, for example, address, revenue, cap rate, and asking price etc. If it's a good deal, smart investor will come to you.
A commercial real estate agent may cost more but if he/she can help you to expose your property to more buyers and get your store sold faster, it might also worth to use them. All at least you say "broker protected" on your advertise to attract agents to bring customers to you if they think its a right property for their customer.
Take care!