Immediately i open my endings book to find theory regarding queen vs queen endgame. One interesting techniques that i found is the" wheel perpetual check techniques"
Black to move
The idea is not letting the superior king left each square next to his queen ( diagram below)which is in this case the c4-c5-c6-d6-e6-e5-e4-d4 square or wheels! 1...Qd2+ 2.Kc4 Qa2+ 2...Qc2+? will let the king left the "c4-c5-c6-d6-e6-e5-e4-d4 wheel" ! 3.Kc5 Qa5+ 4.Kc6 Qa8+ 5.Kd6 5.Kd7?? Leaving the wheel will of course lost the queen 5...Qxd5+ 5...Qd8+ 6.Ke6 Qg8+ 7.Ke5 Qg5+ 8.Kd4 Qd2+ ½–½