My honest opinion for being adept at parrying in this game, assuming conditions aren't laggy?
Play some dark souls.
Seriously! I may be laughed at but I got the hang of it pretty damn quickly, coming from parrying in that where the animations are important and enemies even try to fake you out.
If you need to stay in kf2 for this, then you want to spend time getting hurt by what you want to parry. Pay attention to the animation of the enemy and at what point it hurts you.
You also want to get timing down for the weapon you have in mind, the hammer raises and blocks slowly for example whereas the katana seems pretty quick with it. In a server with 50-60 ping? I'd say parry on the second half of their windup instead of their attack. This is all just me though, only bit that's not unique to me is spending time experimenting with it.