ᐅ Second coat of lime plaster is setting too quickly – what can be done?

Hello everyone, we applied a layer of pure lime base plaster, about 10mm (0.4 inches) thick, on a pumice stone interior wall (well moistened beforehand, house built in 1930). Afterwards, we kept dampening it repeatedly over several days. Now we want to apply a fine finishing plaster, also pure lime plaster, but it dries too quickly despite the wall being well moistened again! Does anyone have any tips?