Walter - not overly fussy. This is not cut-and-dried, but it is definitive.
First of all, shihan was originally a title to designate someone who was authorized to teach the entire curriculum of a classical martial tradition. For example, I am a shihan (instructor) of several classical systems (koryu) - this doesn't mean that I 'teach teachers' - it means that I can teach the entire martial tradition from beginning to end and am, in fact, authorized to extend the tradition to another generation.
One should never call someone shihan . . .. as in "Amdur shihan" - and no instructor should allow her or his students to do so. It just sounds . . .off . . .like you refer to your university professor as "Doctor of Philosophy Professor Amdur"
On the other hand, someone quite properly could have a name card that has (using myself as an example again). "Ellis Amdur, shihan, Toda-ha Buko-ryu" or in some traditions, adding the generation as in "Ellis Amdur, 19th generation (代) shihan, etc." Others omit the 'shihan," and just put "19th dai" either because it is obviously implied, or the particular school doesn't use the term shihan.
You would never put, for example, "19th dai sandan"- the term is confined to a lineage holder.
There's been a lot of talk about this in aikido circles - and I don't know the current official opinions and rules - but shihan used to be someone considered a genuine master instructor.
The safest thing to do is simply call anyone you respect and who has authority as 'sensei' -