Ya, I have no idea how someone parallel parks a manual (w/out hill assist) on a 15% grade; I personally have to keep one foot on the break and one foot on the accelerator!
You can use the e-brake as you lift off the clutch pedal and press on the accelerator. With some learning, I'm now pretty OK at it after some 13,000 miles of manual driving total.
It is possible, I've driven manual cars and trucks from 1995 to 2010, no accidents whatsoever, but sometimes you want it easy.
You just use the handbrake as necessary. I mean, it's not necessarily simple. But very much possible.