I want a brush with a variable rolling width and speed, and variable flicking.
My idea is that when rolling straight-on, your trail is very thin and you run very fast, but turning slows your momentum while widening your paint trail. While going in a straight line, you don't deal rolling damage and you barely get deflected when you do hit someone while rolling (just enough to slide past the other player's hitbox). Not only will you hear the invincibility ping when this happens, but the player you just hit will have a few i-frames. However, its max rolling width would deal 105, so you could splat an opponent with a sharp enough turn (probably something like 120 degrees).
As for the flicking, each time you flick the brush, the windup gets slower but its damage and range increase. If you were to get the drop on someone and hit them with your lowest range weakest shots, it'd take about 5 shots to splat them, while your farthest slowest swings would only take about 2 shots. The damage fall-off of each shot would scale with whatever the brush's maximum range was at the time the shot was flung. Cooldown for refilling your ink tank would also scale with rolling and flinging such that it takes longer to refill your ink tank the more ink you've put out.