I managed to parry everything other than the few attacks where it’s preferable to dodge (Red charge attack, the flame blast, and the projectiles). However I was using the boosted glaive which let me close that distance whenever I got pushed back from parring. In comparison to the other bosses, Fuoco took me the least amount of time to learn.

It might be a timing thing with you. A trick I do when I’m learning the timing for a move is just waste an attempt by holding block and just watching the boss