But what about the radiation pressure of the Sun ?
Basically radiation pressure consists of two parts: the pressure caused by the incident light wave and the pressure of the recoil due to a partially reflective surface. In the case of a perfect reflector the total pressure doubles compared to the pressure on a totally absorbing (black) body.
If the incident and the reflected wave are at an angle to the normal to the surface, the pressure will be proportional with the square of the cosine of that angle.
Now imagine 12 mirrors placed along the equator of Bennu, 142 meter apart from each other, with a circumference of the asteroid of about 1700 meters.
For simplicity of calculation each mirror has an area of 100 X 100 m$^2$ and can rotate along its horizontal axis and is facing eastward.
Since Bennu has a retrograde rotation, the left side of it turns away from the Sun, so to get the asteroid rotating faster by radiation pressure only on the left side the mirrors will have to reflect the sunlight.
On the right side of the asteriod the mirrors should be turned in such a way that almost no sunlight will fall on them to prevent radiation pressure being exerted upon them then.
Will indeed Bennu rotate faster and faster this way and can it be roughly calculated how much ?
To make the calculations somewhat easier, only the force on one mirror at any time is asked for, namely during the time interval when the angle of the incident light wave with the normal of the position of the mirror on the surface changes from 60$^0$ to 90$^0$.