What is the process or material that can enhance the conductivity of the graphene oxide?
Addressing the problem of high resistance, we can identify that the resistivity derives from the oxidation of graphene, changing $sp^2$ carbons to $sp^3$ in the lattice, which increases the band gap, and creates an insulator. There are a number of answers to this question that could be correct, including simply mixing another, more conductive material in the synthesis, but since the question seems to imply that the material has already been synthesized and simply needs to be reduced, removing the oxygen, creating reduced graphene oxide (rGO). One simple approach is through thermal annealing, where GO is reduced by a heat treatment.

You can read more about the reduction of graphene oxide here.