Keep up the antibiotics and don't be in a hurry - she's had a long-dead lamb and it can take a few days.
BH has farmed sheep all his life, we have 200-300 breeding ewes now but in his younger days they had double that. He won't remove cleansings himself, always gets the vet to do it if it doesn't come away after a few days on antibiotics. But we have the economies of scale, and can spread the cost of the odd vet visit across so many more lambs.
BTW, if the vet stitches up a ewe who prolapses before lambing, you have to snip the stitches when she goes into labour. That's why I like to try the prolapse spoon first - she can lamb through it. Prolapses after lambing are bad news, in my experience.