How to introduce a male bull mastiff to a male staffy? HELP!?

IMO, it was an idiotic thing to get a male bullmastiff when you already have a male staffie. Both of those breeds are prone to same-gender aggression and no amount of socialization, training, or neutering will change that. Call your local animal control officer and re-home the new dog. If you get another dog, for goodness sakes, make it a female and have them both fixed.