Why did you help him? Was he in distress or he just internally pipped?
I'm not familiar with ducks, but if it's yolk sac is still attached than it sounds like it wasn't ready to hatch.
Here's a good link on assisting chickens, I'm assuming it runs very much the same for ducks:
Step by Step Guide to assisted hatching
Keep that baby moist. If you don't have an incubator and only have a heat lamp, wrap the egg in a WARM wet paper towel and keep the membrane very moist.
If it has a hard glue like material covering its feathers, it sounds like it is very dry.
Humidity is crucial, as is warmth.
Make sure that baby doesn't rupture it's yolk sac. Make a small container And let the baby rest, don't let It walk around too much as it will hurt its yolk. He needs to absorb that yolk.
Good luck.
Edited to say: I can't get that link to work. Type in the search bar "assisted hatching" it's a byc article, you should find it.
