I liked this 5 video playlist by Louis Rossmann https://www.youtube.com/watch?v=CI9Z_fJ38lM&list=PLkVbIsAWN2...

He is an independent repair technician/youtuber/right to repair activist, and not a guru of some sort, and he's speaking from his experience here.

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Salesmanship part 1 - Don't present without knowing the priorities of the customer

Salesmanship part 2 - Don't be NEEDY just because you're a salesman!

Salesmanship part 3 - Focus on the PAIN & MISERY of your customer!

Salesmanship part 4 - Give people MULTIPLE CHANCES to SAY NO to what you are offering.

Salesmanship part 5 - The customer is rarely RIGHT, but ARGUING always makes you WRONG!