It's one thing to ask a friend to feed a cat for a couple of weeks, quite another to ask them to empty a litter tray for a couple of weeks. It always feels too much to ask, IYSWIM. Like asking them to clean your loo for you. So my solution is to pay a local teenager to do it - if a bit of money changes hands, dealing with cat shit is OK. This was only at kitten stage - lucky not to have absconders.