In addition to Gordon, a common practice was for local fully competent modellers to enlist on those cheap courses just to use the larger/better machines, but overwhelmingly to machine cast iron, to avoid cleaning their own machines of the grinding paste chippings!
I went on one (I was unemployed at the time, so reeelly cheap!) and found there was no real teaching – just having a project and being put right after one had gone wrong!
If you find a course, see if there is any formal demos or if it is just an "overseen" collection of users.