The reflective equilibrium method is the right kind of approach (and I should have mentioned it). In addition, I think that without independent justification you can only take a general principle as far as your intuitions about it take you. So we might have a general intuition that consequentialism is right-- but we can't just assume that contrary intuitions about particular cases are wrong. All else being equal we should prefer theories that get intuitions about general principles and intuitions about particular cases, right.