I'm not that great at photoshop, but um I hope I can help :D.
You could try duplicating the sprite layer (maybe more than once). And set the duplicated layers to overlay or whatever you prefer. I've never tried it, but that's what I would do. If that makes the sprite look even more messed up xD, then maybe you should manually blur out the pixely spots :o. I don't know, just my suggestion

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ps. I really like your signatures :o They're very pretty