The basic strategy of this is simple. First, you should master shifting hollow. After first boss, you put on Promethus blood code. You'll wear this for bosses until you get Heimdal. The major gifts to look for are poison, Fatal Surge, Cleansing Light, and Bridge to Glory (only available after Successor of Throat). Use Atlas Chrome on veil and Eos Chrome on weapon. I suggest two weapons, a poison and a gift.
Other than that, shifting hollow for glory. Most bosses crumple quickly. The only tricky ones to do solo, flawless are "Not Ornstein and Smough" and Virgin Born--because of nuke.
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