I get mine at any hobby store and use the thick gel. The thin stuff runs to much and you'll end up glueing your fingers together like one of the other reefers who posted a comedy routine in her blog about that very thing.
Even with the thick stuff however you still have the potential to glue your fingers together.
What I do is apply a small bubble to whatever I'm mounting, and put it on the rock (this is for zoas) return the rock to the water and volla you have a mounted zoa. But when cutting zoas it is
important to note that they have a chemical on them that has caused people to go into a coma and/or could cause death. So
WEAR GLOVES.
The zoa will be ticked off for several days if not a week after this procedure so don't expect it to open up right away and be happy.