Or if you want to just change a single piece of the kit - in this case a snare using brushes...

click on the label under the picture of the piece you want to change.
In this case the piece using brushes has [Br] suffix on the description.
Something to possibly keep in mind it that Kit settings will affect the sound of the kit pieces.
So if you are using an effected kit or arena kit the effects or reverb will also be applied to kit pieces even if you change the pieces.