Even though they have spun the cocoon the pupation process is not complete. The cocoon should not be handled or reoriented for at least another week as this can cause problems and the moth may not be able to emerge from cocoon properly.
I have never raised this species, but you can force a diapause by chilling in the fridge or outdoors. Your best bet it to put a couple layers of paper towel in a plastic gladware type container, put a couple of drops (you want ONLY enough moisture to keep it from drying out DO NOT wet the whole towel), put the lid on tight and place this in the crisper part of your fridge. the temps stays more constant and will maintain better moisture. I have a friend who knows more about these and will check with him on duration of time and get back to you.
As for the sphinx moths, you should be able to do the same. Where do you live? Are you in the UK?