Unfortunately, there's no quick solution to de-boning trout. The best method is to remove the entire backbone, along with the ribs.
To achieve this place the fish skin side down and with the point of a sharp knife, gently work along both sides of the fish freeing each fine rib bone. Once they have been freed from the flesh, you can cut around the spine (try not to break the skin) and remove the whole lot.
If the fish has been filleted, then lay the fillet flat and with a pair of tweezers work your way front to back, extracting the small bones as you go.