Are there any poohs in his side of the house? Has he got a pooh stuck in his bottom? Our GP2 frequently has a walnut sized turd in his lower regions. Poor little thing, passes gas and eventaually we find it in his bed.
Vaseline round his bits ? Plenty of watery veg like cucumber and celery if you have them. Maybe some grass if you can get hold of some.
Is there any chance he might have eaten something like plastic or cellophane? Keep a check on his abdomen. If it feels tight, bloated and 'hollow' if you tap it then this points to an obstruction. If it's obstruction, it's a vet SOS situation.
Hopefully it's a big pooh that he'll pass out. We sometimes 'help' GP2 with a baby wipe. Not too often though, I don't want him getting lazy