You might have asked that question in that thread? or there may be alternatives in that thread.
I have used a SLIGHTY (not drippy at all) q-tip with isopropyl alcohol on it, touch to the trackball and wipe gently with a lint free cloth, like a eyeglass lens cleaning cloth.
I have also touched it and wiped gently with an alcohol wipe that is not very moist. Let it dry a few seconds after taking it from the package.