This is the most frustrating slave cylinder in have changed.

First new slave, plastic piece fell off inside the transmission. Got a borescope from AutoZone and then then scope tip fell off. Managed to get both out. Got a new slave and the rubber grommet thing came off when I was trying to bleed the system. I have tried a hand pump bleeder with no luck, and I keep messing up the cylinders when I try the gravity bleed method. Working on a 3rd slave, any tips?