Walter;
Unless there is a specific need to find the queen, you need only to
confirm her being there by seeing properly laid eggs.
However, if you need to find the queen(eg. to replace her), I might
suggest placing a queen excluder between the two brood boxes, returning in
3 or 4 days, checking for eggs. The box with eggs in it should be the box
with the queen. Once found, she could be marked, making things easier in
the future.
Light coloured queens are easier to find than darker ones.
Queen location is a challenge.
Good luck :)
KBF
PS. As with all things in beekeeping, there are several ways to solve a
problem.