Honestly, if device wasn't liquid damaged I ripped pads to the point which makes device unrepairable maybe 2 or 3 times in my quite long service career. But I was soldering for first time when I was 12, started to fix the mobiles when I was 16.

I soldered my first sandwich SoC (simple reballing because of the liquid damage, few pads was corroded and solder ball popped out from the chip) at second try, that was Nokia N73. Everyone in the service was astonished because device worked for first time. Later when there was more devices like this we had a lot of donor boards. We just limited ourselves to one try at unit.

Forgot to mention: I was using an universal stencil and good solder paste instead of balls. Good paste has also good flux so makes the process much easier. I'm using this method even today when I'm reballing some chips in macbooks, mostly RAMs and SMCs.