You need two "specialized" tools, a lockring tool to fit your brand of cassette and a chain whip to hold the cassette stationary while you unthread the lockring. A big open end or adjustable wrench will be needed to turn the lockring tool but there is nothing specialized about it. A lockring tool with a center pin is steadier if you have a quick release hub.

BTW, you really don't need to remove the cassette to clean it. It can even be done on the bike without removing the rear wheel but it's easier if the wheel is off the bike. Just get some rags and a little solvent like kerosene or mineral spirits.. Dampen the rag with the solvent and "shoe shine" with it between the cogs. A few minutes and the cassette will be sparkling clean.