Personal comments from a small farmer:
If the ewe is rejecting its lamb, or in the rare case when the ewe dies but a lamb survives, you may be lucky
and have another ewe which has just lost its lamb, or has a single and could cope with an extra foster lamb. We use a saucy strategy.
We put the foster mother ewe and lamb/s into the ex-chook shed/ hospital ward. If the ewe's own afterbirth
or dead lamb is still around, we pick it up and rub it along the foster lamb's head, back line and particularly under its tail - the places that get sniffed by the ewe.
Disposable gloves make a messy job easier. If that isn't an option (or for the next feed anyway) we dribble sweet soy sauce along the same areas. Homebrand sweet soy sauce is
cheap, and it goes a long way. Sweet soy sauce is salty like ordinary soy sauce but with molasses in it. Salt and molasses are ewe lollies, and the ewe will lick the lamb.
H holds the ewe, W gets the lamb to suck, and with luck it all comes together. If the ewe has her own lamb as well, we sauce both of them so she gets them mixed up.
We have small grassy areas outside the hospital wards, so we let them out to graze in the day time and put
them back at night or when we need to do a feed. We keep them prisoner and use the sweet soy sauce until the lamb is smelling like the ewe, which takes about three days.
Use disposable gloves and wear washable clothes - sweet soy sauce goes everywhere!