I have successfully washed Vagabonds cushion covers in a domestic washing machine at 30 deg ser at high speed spin. I don't think they shrunk although they were a little difficult to get back on to the foam cushions aftewards. I did not iron them!
The wash got them clean and also took the salt out of them. However, as the cushion had been soaked in sea water, the salt remained in the foam, so even when these were thoroughly dried the salt absorbed water out of the atmosphere and they soon felt damp again.
