Honestly with using high build filler primer it was pretty easy. Really just sanding the primer down to get it even. Did 2 initial coats, little wet sanding to see how it looked, then a 3rd coat and a bit more wet sanding.
I went and tried the Purple Harmony pillow when there was a similar thread on Reddit ~1 year ago. It was fantastic! I wanted it sooo bad, but it was just too expensive. I did find out later that Purple runs sales a few times a year. Think the best was around Christmas and it was damn near 50% off. So, I've had it since Christmas and been very happy.
Honestly with using high build filler primer it was pretty easy. Really just sanding the primer down to get it even. Did 2 initial coats, little wet sanding to see how it looked, then a 3rd coat and a bit more wet sanding.