They sell to many other customers and they know what the smart operators do. Perhaps those managers have long ago solved a problem that you may be facing right now. Suppliers are usually glad to share this information with you, at no cost, so you don't have to reinvent the wheel. Business friends can be another source of good advice. You'll be getting counsel from successful people that you trust, and advice that is likely to be pretty good and free.
Technicians are expensive.
But some of your men or women business lunch friends may well be a current or former engineer, architect, economist, or chemist. You might even bring one of your people to the lunch and discuss problems and solutions. Advertising agency officers often get to know their clients quite well. This is good for both parties. It saves time for everyone and leads to more efficient programs, plus an enthusiasm that can generate that little extra plus in the marketing strategy.