I use oil, too. But i regularly put them out and clean them.
Choke tubes never seal up 100% at the bottom, so there is always debris around them.
So cleaning them before they "bake" in
is a good advice.
Same here. Bought one for the shotgun and one for one of my rifles to set up the scope roughly. Did not work at all.
The one for the shotgun can be used for some indoor training, but that's it.