Based on the recommendation of a posting in this newsgroup, I got a quart of
Zinsser's Bullseye 1-2-3 primer.
This is a water-based primer which will adhere to practically anything,
including glass. It certainly lives up to its reputation, because if it
dries on your hands you just have to wait for it to wear off.
It makes me wonder if it doesn't adhere TOO well.
If it became necessary to remove the paint, would ordinary paint-remover do