I go with mugen and jin. With the church being so big, they can find a way to separate spike from vicious and disarm him. Both are better swordsman then vicious, so if they can get to spike up close, they'll be fine. I never saw mugen or jin deflect bullets, but they have good enough reflexes to stop sound waves, so they can at least dodge bullets to get in close to spike. Hand to hand shouldn't be a problem for mugen or jin, they both have attack speeds above vicious and spike.
I mean yeah, but only once in the entire series and it was never explored again, and he was in far worse positions where he was never able to use it again.
I think they're capable of deflecting bullets, it just have to be large gap in timing during the fire. They were never pit in danger forwards a firearm up close, so we'll never know if they can deflect bullets, but shoryu's wind attack was pretty fast, mugen was able to dodge and deflect. He saw the wind attack and countered it, disarming shoryu. The velocity of the wind must be great to cut through a human being. A test pilot was able to take 457 mph wind without getting injured. Shoryu wind attack should be moving faster.