Force feeding tails isn't too stressful. If you have a baby who won't tease feed (kind of rare) then cut a piece of weanling or adult mouse tail, about 1.5 inches in length, thaw it, wet it, gently open the snake's mouth and insert the thick end of the tail. I twist it to help it go down rather than just pushing. Often the baby will start to swallow himself. I try to encourage this.
I keep going through my list of tricks, on a 5-7 day interval, and then, if the baby refuses as expected, give him a mouse tail.
For tease feeding, are you doing it "right?" I hold the baby about an inch down his neck, and _jab_ him with the pinks head, to get him to strike. It works better if you jab him in the neck, not the nose or face. You often only get one or two chances, so you have to have the pink's head aimed correctly. It's easier with a boiled pink. Most babies will readily strike multiple times, and once he connects with the pink, freeze. He will either proceed to swallow, or drop it. If he drops it, keep trying until he stops striking. Once he takes it and holds it, you kind of have to get a feel for the next move. If the baby is difficult to get to strike and feed, I will keep a somewhat tight hold on him and let him _barely_ creep through my fingers, since they often drop if allowed to run with it. I also keep them from touching any surface. If the baby readily strikes and proceeds to feed, I will hold more loosely and let them crawl down to the feeding surface if they want. Make sure you are in a comfortable position before starting, because you may have to be there for a long time. I like to sit at a desk with something to rest my elbows on. I think I used to be less successful with tease feeding because I was less aggressive about it. They call it "slap feeding" for a reason. Also- most baby cornsnakes will instinctively bite if touched in that certain place on the neck, about an inch below the head. Take advantage of that reflex.
Also- just because a baby refuses one type of dish soap, that doesn't mean he will refuse others. Ivory, followed by Dawn, are the most successful, but try those two plus others. I have a Dawn eater right now who refused Ivory.
You might want to try, carefully, the water deprivation method. You can take away the water bowl for a couple days, and then offer a soaking wet pink. I'd make sure the baby is well-hydrated, by soaking, before removing the water, so you have a known starting point.
I have two non-feeders from the end of June who have only had two mouse tails each. They are maintaining their post-shed weight all right. I'm nowhere near giving up, though I am starting to get a little frustrated. I lost a baby who was very dear to me by not being aggressive enough in feeding attempts- by slap feeding or forcing mouse tails, and it will never happen again. It seems hopeless, but I have _never_ had a baby I commenced force feeding not go on to become a normal, eager feeder eventually. It often happens a lot sooner than you'd think. And tease feeders are quite common and fairly easy to wean off tease feeding.
Another thing to try is, back off your attempts to every 5-7 days, and get a tail down them so you at least get some calories in. Maybe two consecutive feedings of tails. Then re-cycle through the most successful tricks- boiling, Ivory, Dawn, tuna water, chicken broth, and if the baby won't take it in the deli cup, then leave the pink in the baby's bin overnight, possibly in a squished TP roll hide. I've had a number of babies who just will not feed in a deli cup, but who will reliably feed in their bin, overnight. Alternatively, if that doesn't work, try them in a deli cup overnight.
