Training is necessary but that is a high cost. Also bringing in someone from the machine supplier may not be effective because they will probably be expecting some level of knowledge on the part of the people they are training.
I suggest trying to find someone local who will come in on a contract basis and give both group lessons and individual tutoring starting with group lessens intensively for a few days and then changing to a few hours per week for a month or two.
This was my approach when I switched my shop from all manual machines to all
CNC and it was very successful. An important aspect to the training is that until the workers have had some introductory training and started doing some machine work they do not know what questions to ask. This is why you need the intensive training for a short while then a follow up in greater depth over a longer period.
And I must disagree with Shotout about hiring someone;
contract with someone to do the training. If you hire someone you, the employer, are responsible for making sure they do their job and if they are inadequate you cannot easily terminate them. With a contract the Contractor is responsible for making sure they do a good job. You can specify goals in the contract and if they do not meet these goals you can terminate the contract and not waste money.