How to manually locate a certain declination in the sky for a given location? (no sextant available)
Jacob's staff is probably all you need.  It is a pole with a cross arm. By positioning the arm at a certain point on the pole and sighting down the pole one can get a position on the sky.  A skilled user can achieve sub-degree accuracy with such a tool.

The position of the cross beam is easy enough to calculate by trigonometry, or by careful construction of triangles.
$\tan(\theta/2)= c/2l$
Where $\theta$ is the angle above the horizon, $l$ is the position of the crossbar from the eye and $c$ is the length of the crossbar.