Spectacles only fog because exhaled air escapes from under the mask. A basic mask called a FFP1 which you are supposed to wear on public transport to avoid your droplets infecting others is not tight fitting and will fog
If in the future you are in close proximity and wish to keep yourself safe then you need a higher level mask called a FFP3 which creates a seal around the mask. Properly fitted it cant fog.
Many HEMS units use reusable rubber masks. You must ensure the filter is a P3 filer and not just a dust filter, but if both instructor and student wear one they are both safe from each other. You still need to wash hands especially after removing / touching the mask.
Of course this assumes there is still a risk of infection when training resumes