Best way to thin out a neck?

Posted in Custom Workstation

Real simple, I am working on a project, but i noticed that the head sculpts i acquired dont fit well on the neck of the base figures. The neck just looks too fat for the head sculpt. The base figures are neca terminator figures. Im curious on what would be the best way to sorta thin out the necks a bit to make the heads sit and look a bit better?