Well that's one way!

For a simple approach: First, make sure you are turning in the correct direction. Second, a cheater-bar tube for extra leverage over the wrench should help. Third, mildly heat the area, because if held in place with anerobic thread-locking adhesive (Locktite), that stuff softens at around boiling water temperature. That would be my first approach, boil some water, pour on, promptly attempt to remove. Now, with steel frame, easy. Aluminum frame can begin to lose strength at surprisingly low temps, so would not heat hotter, but has the plus of a higher coefficient of thermal expansion than steel, so given same delta-T, should loosen a bit from the steel bottom bracket cup.