If you're sure you can't use the skinning or wetting the lamb try rubbing the new lamb at the back end of the ewe as she will be wet there from the lambing fluid and it will transfer some of the ewes smell as well. Also rub both lambs together to merge the smell.
It also helps to stimulate the ewe by sticking your hand inside (when you remove your hand she will think she's had another lamb) and then present the new lamb to her, put it under the her lamb. If the new lamb gets up straight away your ewe will know its not hers.
If you're ewe is older and more experienced and likes treacle rub some on the lamb, she will greedily lick the treacle and the instinctively start licking the lamb.
Adopting the new lamb will only work if the new lamb accepts the ewe if it has a strong bond with its biological mother and a few days old you run into a whole set of other problems.
Good luck,

if you do it has to be done straight away.