How is this routinely done?
No idea but I just tried the X25 that I inherited from my father in law.
The split ring should be driven towards the handle with a square edged tool until it is clear of the tip entirely.
I used the handles of a cheap auto crimp tool, tap tap tap.
The tip then easily slides off and the split ring that has an enlarged leading edge can be driven back onto the tip after installation. The shank of the tips on these get a bit rusty so a clean up with some emery will help refitting of the retaining ring. Install it just to the slots in the tip and tap the ring down most of the way to the handle after installation onto the element.
BTW, I've just done this ^ and the process of reinstalling the ring cleans the rust from the outside of the tip quite well.
The element on this one was as clean as a whistle and quite smooth so if it needed a clean up you'd want to use some fine wet and dry, say ~300+ grit.
As for locking on prevention, it need be clean and if tip replacement was regular I'd use nothing.
Otherwise from my kit of tricks......copper based anti seize, nickel based antiseize or good old plain graphite powder, take your pick.
Edit.
With little effort a hollow tool could be made to drive the retaining ring off the tip while HOT and then just invert the iron for the tip and ring to fall off.
I'm beginning to like this old Antex.