I operate a business similar to your for extrusion, however it is marketed at a higher technical level, as I don't "setup" the extruders in the hands on sense.
Selling technical expertise can be difficult. There is a model for selling technical expertise, and that is consulting firms. However the type of technical expertise that is sold by consulting companies is at a much higher level than machine setup and operation. The closest to what you are trying to supply are contract maintenance workers. Those services are sold based on reputation and availability. Think "Joule". The maintenance workers are also much more general purpose.
You need to demonstrate the value of your service to your prospective customers. Since most of your customers will employ setup people which they are already paying for you need to demonstrate how working with you in addition improves their bottom line. Your web site proposes firing those high priced setup people and replacing them with your services. This is a big set for a company because that setup ability is core to the company. If I owned an injection shop, I would not fire my core competency, period.
On the other hand, companies will find themselves without good setup people from time to time. Then you can step in. You may even be able to offer setup people on a contract basis and then convert them into a full time hire, collecting a fee for both activities. Perhaps you then become an unemployment to employment service for IM setup people. Recruiting fees collected can be significant depending on what you negotiate. Having setup people has value; if you can manage the transition periods for companies seemingly that provides a lot of value for companies in need. Yyou might be able to make a good living by filling that need.
“If you IM setup person quits today, we will have a competent technician there tomorrow to keep you running.”
If you agree with such a business model, then sales, marketing and business practices can be developed to support it.