Roger's and Shanks' crew are displayed as using fighting styles as random as possible. Sometimes blades, sometimes guns
Sometimes one blade, sometimes two like in Rayleigh's case, and also not dedicating oneself to one weapon but switching them (given that blade Rayleigh is using is different from the one he used against Kizaru).
This is by definition a Hakiman. Someone who doesn't use one particular weapon. Rather the weapon of choice is just a tool you channel your Haki through. Note how Roger's slash sent out a blast of Haki. Not just a flying slash.