Have some questions about infusion/buff miracles

So I just managed to get the dark blade miracle and am working towards acquiring the sunlight blade and I had a few questions. When you infuse your weapon to be blessed or sharp do you lose the ability to use those weapon buff miracles? Right now I'm running the uchigatana and have a dex/faith build. What infusion do you guys think would work best? I wanted to do blessed but it lowers my Dex scaling for the weapon. Not sure if that's a good idea or if there's another infusion that would be better. Any help is appreciated. Thanks