With the brush tool, select the round brush (size can decide for yourself), press F5 to open the brush settings to select the dynamic shape, from top to bottom of the first control to change into a gradient, the latter value can be changed to 50 (if the effect is not ideal can then change the value), the minimum diameter of 1%, the other control off the value of 0, at this time, you can see that the shape of the brush has been issued to change the brush off the brush settings in the canvas! directly on the canvas after closing the brush settings, cross the two strokes of the two strokes can be, try