If a jar is being used as a trap, it’s important that the entire outside of the jar is covered with masking tape. The tape must go right up to the rim of the jar, or the insects will slip before they enter it. The jar shouldn’t be too tall. Using a fresh sample of bread that is quite big should also be helpful.
Some people use a rolled-up newspaper for a trap. An elastic band is loosely placed around each end of the roll to enable it to keep its shape. The newspaper is then moistened and placed where silverfish are likely to be. The plan is for the insects to enter the dark interior of the roll to feed on the newspaper. I don’t know how effective this type of trap is. Some stores sell commercial silverfish traps. Any type of trap may need to be used for several days before the insects discover it.
Traps work best at night when the insects are most active. If you can see evidence of the insects’ activity, that’s a good place to put the traps. It sounds like you’re already doing this, though. If you try the techniques that I've described and you still have a silverfish problem, it might be a good idea to contact a professional pest control company for suggestions.