Method #1: Suicide Rush - To prevent build up of carnavons/dust zombies from occurring, concentrate all your attacks on the Black Kat until it dies, ignore everything else, including dodging. NOTE: You will likely lose a lot of HP or even die.
Method #2: Discriminatory Attack Method - To prevent build up of carnavons/dust zombies from occurring, concentrate all yoru attacks on the Black Kat, until it dies, but try to avoid getting damaged if possible. If required to do so, charge attack spam.
Method #3: Rid the Pesks and Distractions - Destroy any monsters that'll likely cause huge problems for you while taking on the Black Kat, occasionally striking the Black Kat when possible. Then rid the carnavons/zombies later. Note: This might cause a large build up of dust zombies and carnavons.
Method #4: Take on the Army - Just attack and dodge everything, until the everything dies. Note: This may take a while.
Method #5: Divide and Conquer - Have people do different jobs. One person get rid of the carnavons and zombies to prevent build up. Another person take on the Black Kat. If there are more people, they can do candle lighting if you're in Candlestick Keep and/or rid the other enemies in the area. Otherwise, join in to slaying the Black Kat(s) or summoned monsters.

Just a bunch of random stuff I came up with. =P