Strictly press on in my experience, although I imagine there are those who use glue when the bezel is loose. I doubt its in the Omega Manual to use glue.
Replacing bezels is one of those things that when it goes smoothly, I think any fool, especially this fool (me) can do it.
I even made a video:
What I have learned since:
The tolerances are extremely tight. What we are looking for is a "click" onto the case. Sometimes the bezel will seat without a click but be perfectly fixed. Other times, no matter how hard I press, it won't go on. Sometimes the bezel is too loose, and sits in place with no friction, or too little to hold it safely.
Sometimes a bezel fitted to a speedmaster can be popped off and simply cannot be replaced again without "adjustment".
In my experience it is worth giving it a go, but after three attempts I send it to the watchmaker - and I am really strict about that. If I can't get it on after three goes, then I send it off.
If it goes onto case too easily, I send it off.
Lastly, my poker chip method works for me. Some watchmakers have expressed concern at my method, and they may be right. Simon F uses a knife to twist it off, something I have never been able to master, or even bring myself to attempt for fear of damage.
Lastly lastly, make sure you use the right size press. (Obvio I know, but its important)
Good luck
