Here's how I build the Corally shocks.
After you drain out the old oil...
1. Pull the shock shaft all the way down. Fill the shock with desired oil till you see a little dip in the surface at the top. It should be nearly at the top, but not quite.
2. Slowly bring the piston to the top of the oil, but not through the top. Then bring it back down to get rid of air bubbles. They'll float to the top. Repeat till there are no more bubbles.
3. Push the shock shaft in about 1/3 of the way. Place the bladder on top of the oil. Pull the shaft down to create suction, which holds the bladder on. Screw cap on.
4. Shock should rebound a very small amount and slowly. If it rebounds fully and fast, you have too much oil in the shock.