I’m going to highly recommend against assist/force feeding 1000 gram snakes that have ate many times in the past.If they are all refusing food it would be a indication of husbandry problems imo. Assist/force feeding a snake that size is never an option in my mind. A pinkie or fuzzy would not be enough nutrition for a snake that size anyway. All 5 snakes are not eating for a reason forcing them to eat won’t change the problem that is causing them not to eat in the first place.
Nobody is suggesting to let the snake starve just fixing the problem that is causing them not to eat. Forcing a rodent down a snakes throat is likely to cause more problems that it solves you still have a snake not eating on its own. A 1000 gram snake will not starve itself unless there are underlying health issues. If your having to force feed a lot of snakes the issue is likely not the snakes themselves but the conditions they are kept in.