Separate spheres widely.
Connect them with a long wire.
Charge the system.
Remove the wire.
Now you have two spheres at the same potential and sufficiently isolated
from each other to allow a closed form calculation giving:
Q1/R1^2 = {Q2/R2^2}*{R2/R1}
IOW the ratio of the surface charge densities is the inverse of the ratio
of the radii. Check my math :)