I want the brush to have a sharp tip

Wait, i had the same problem just a while ago, and i figure it out recently.. 

so, first you need some pen tablet or display tablet, both are needed for the pressure sensitivity, then open the brush setting, you can open it in window -> brush setting / (F5) then go to shape dynamic - control and change to pen pressure.

And yeahh... you can have a pointy brushes, maybe you can adjust a little bit like you want to make it more comfortable for you work with that brush.

Use a pressure sensitive pen and tablet, start with low pressure, increase pressure in the middle of the stroke, decrease pressure again at the end of the stroke.

To get both ends pointed, you need to make a path (not a Shape) that follows the way you want your line to go. Once you have the path, select the Brush, and in the Brush Settings panel, under Shape Dynamics, set the size control to Pen Pressure. Then, open the Paths panel menu (the three lines), and select Stroke Path. A small dialog opens, where you can select the tool you want, in this case, the Brush. Make sure the Simulate Pressure box is checked, and click OK.