synthetic alkyd enamil.
with no hardner, you may be in luck. soak a rag in naptha and give a wipe. could do the same with your reducer.. but check the reducer.. some have heptane and other goodies in it. i'd test those in an inconspicous spot to make sur ethey did not cloud the paint finish.
the fall back is ultra high polishing compound. low removal type. heck. many time simple car wax, buff on type will be enough.
avoid buffing or rubbing compounds.. only wax or polishing compounds.