After trying to get him to bathe in the sink, in the bath, under the shower and with a trigger bottle, none of which he enjoyed we have discovered that a trigger bottle that gives a very fine mist is just what Casper likes.
Here he is having an al-fresco wash:
Casper enjoying an al-fresco shower by Jean-Pierre Declemy, on Flickr
Yes, I like this! by Jean-Pierre Declemy, on Flickr
It has only taken us four years to find out!