Yeah, it is said if dbol is taken only in the morning, it will not supress hpta because it is so short acting. At least that is the concensus...never tried it myself.
I admit I've never done it, and was suprised to hear it, but several have used it successfully for a bridge. The key is to take it only in the morning when natural test levels are high.
Fonz has stated that you can use up to 100 mg/ day, but most use much less.
If your natural test is already suppressed from a cycle, ALL AS will continue to suppress it. The idea of a bridge is to give your body a break from the high levels of anabolics. Not to bring natural test on line.
Once again, you must be clear of all AS to bring natural test online.