Someone forgot to put an "R" in "DS" or "DOOH"!
"R" as in "RESPONSE". We all know that the purpose of DOOH is to communicate more effectively to target audiences where they are---out in the marketplace. Lots of attention has been paid to "communicate", but more attention could be paid to "effectively". Doing that requires a focus on measurable campaigns, calls to action, and selling proposition. DOOH is a fantastic media, but it will become more and more dominant as the numbers come in on effectiveness. And focusing on measurable response provides you the numbers and justification for your selling efforts.
Make sure that when you pitch your solution you recommend Direct campaigns, along with all the other wonderful things your solution can do. It is the key to selling non-marketing-oriented decision makers. Return on investment is a critical component to good business decision making, so be sure to at least have some hypothetical examples of return on investment for your target client.
For example, if you have an automotive dealership client who makes $600 per sale of their mid-range model, then give him an example of a campaign designed to sell mid-range models and how many it will take to pay for your system and show profitability. Seems obvious, I know, but people tend to get excited about the technology, and sometimes forget to build some strong ROI-based financial justification into the sale. Equally important, once the sale is made, work hard to get the client to use their DOOH for Direct Selling or Direct Response campaigns, where they can measure effectiveness. If you don't produce marketing content for your solution, hook up with a quality marketing-savvy content provider, and offer that service. It will build value, profitability for you, and a more satisfied, long-term client. And if you need a referral for content, give me a shout.