Solutions include scraping heavy deposits of paint off the brick, wire brushing the rest of the solid paint off the brick, and burning the residue off the brick with a torch, heat gun or Bernzomatic flame.
Solvents are not good for this purpose because they turn the residue into liquid paint and soak more deeply into the brick. The goal is to remove the residue while still in the solid form.
The last item is to power wash the brick with high pressure (1000-2500 psi) with a concrete floor cleaner material mixed with the hot water of the pressure washer.