I take a pc of sandpaper and wrap it across the small edge of a flat file. Thats just the size that fits the area between the edge of the rim and where there's a line cast into the rim where the bead is glued. I pass the sandpaper over this and rough the finish up so the glue has something better to adhere to. Clean the dust off and wipe down with alcohol or motor spray and its reay to glue. I do this whether its painted or not, but especially if its chromed.
If you glue over paint or chrome, my experience has been it doesn't stay glued long.