turn the brush dynamics on... i think the bruh size can be set to fade from 100% size to 0% size to scale.. a simple two point line , last time i tried to do this - started thin, thickend up in the middle and thinned toward the end.  it may be possible to achieve the effect you want  by adjucting a frew settings..  oh   "stroke  path" is  under  one of the menu's.. tired sleepy...
Zzzzzzz

"I'm in your image, lol, pushing it's pixels"