An initial virgin plasticine-like poly(3-octylthiophene) (P3OT) and this sample modified by annealing and recrystallization were investigated mainly at X-band (10 GHz) and at D-band (140 GHz) EPR in a wide temperature region. Paramagnetic centers with anisotropic magnetic-resonance parameters were proved to exist in all polymers, namely mobile polarons whose concentration and susceptibility depend on the temperature and the polymer treatment. Superslow torsional motion of the polymer chains and layers was studied by the saturation transfer method at D-band EPR. Spin-spin and spin-lattice relaxation times were measured separately using steady-state saturation method at the same waveband EPR. Intrachain and interchain spin diffusion coefficients and conductivity due to polaron dynamics were calculated. It was shown that the charge transport in P3OT is determined by strong spin-spin interaction and is stimulated by torsion motion of the polymer chains. The total conductivity of P3OT is determined mainly by dynamics of paramagnetic charge carriers. Magnetic, relaxation and dynamics parameters of P3OT was also shown to change during the polymer treatment