As most of us have read in Hug's blog about control, it is a trial and error process. If your opponent shields to block your attack, next time you can grab to counter his shield. Yes, mindgames are greatly involved, but we need not stop here, on the ground, for the air game follows the same principles, and the air defense suffers its mistakes more than its ground counterpart.
Lets say the last time you hit your opponent off the stage, he air-dodged your dair spike. So this time, you proceed along the same path as the dair, but never do it, wait for the air-dodge, and punish. Be it a bair, or another dair, your opponent will be hit.
Gimping in brawl will follow this progression, and will not cease as players become more experienced. There will only be more inventive, evasive ways to edgeguard as play continues, and each match will become a series of battles, mind against mind, and when the match ends, a victor shall stand.