In this instance you need to use both Group and Individual rules.

For the users who are trained, make sure on their individual profile the equipment they have been trained to use have been added to the Trained to use section - see image for reference.

For the Group, add all the relevant users, with and without booking privileges, to the same group. On the Group rule section, you need to ensure that you have selected to have a Separate usage schedule for booking equipment without training and that Hide equipment for untrained users is toggled to No. In the second usage schedule (on the right in the below image) deselect all the days, and turn the toggle for All-day to Yes.

This setup will allow everyone in the group to see the equipment that is in the group, but only the trained users will be able to book the equipment. If the trained status changes for any of the users, and you want them to have access, simply add the relevant item to their individual profile (in the Trained to use section) and they will then be able to book the item,