I looked up the hierarchy of our basic human needs and just as I barely remembered from school, they are food (including water), shelter, and clothing. This got me thinking about the hierarchy of the three basic needs of a prospective customer during the sales process.
The hierarchy of a customer’s needs are:
1. They must like the salesperson they're working with.
2. They must trust the company they're considering purchasing from.
3. The product they're considering must fit their needs.
In your case, you must surely have the technicians’ trust, since you see them every week or so, and they probably already have an open account with you.
You’re driving a mobile store with one of the major brands painted on the sides or you’re an independent selling a major brand-name product. Therefore, the technician most certainly trusts the brand you are presenting to them.
So, in the end, it comes down to two things: How well your demonstration conveys all the features and benefits the product has to meet their needs; and how well you close the sale.