Can't help you with attaching it to a Zeagle.
I've tried three different SMBs, and to my chagrin, liked the Halcyon one the best. It's the easiest to inflate, although the elastic is hard to manage until you figure out that the best way to deploy it is just to yank it apart.
If you aren't doing it for a class, I'd suggest loading the SMB on your spool and keeping it that way. Put the loop at the end of the spool through the D-ring or ring on the SMB, and then pass the spool through the loop so it locks onto the SMB.
To deploy, pull the mess out of your pocket (you do have pockets, right?) and clip the double ender off on a D ring somewhere. Unroll the SMB away from you until it's out to full length. Get slightly negative, tilt a little head down, and inflate the SMB with a full breath. Look up in both directions and let go of the bag. If your spool is Delrin, you can just watch the SMB head for the surface; the Delrin spool will spin out and stay in front of you. If it's stainless, you'll have to keep it in place with your fingertips. Once it reaches the surface, clip the line off to the spool with the double ender.
Pitfalls are getting the whole assembly too close to your body, so you have a risk of getting caught in the line and dragged to the surface (ask Rick Inman about that); not managing your buoyancy properly so you end up positive once you've filled the bag, and while you are still holding onto it; not looking up, and releasing the bag into another diver or other obstruction. Or you can do what I watched a novice diver ALMOST do, had I not stopped him -- deploy the bag, fill it and release it without hooking it up to the spool . . .
