DS was given one of those hideous slimy slugs that you throw at the window and it crawls down 
He has managed to squash it between a couple of books on his bookcase, moved the books around etc etc.
I've tried:
wiping it off with kitchen paper
multi-purpose wipe
neat detergent/kitchen paper
window cleaner
Still slimy. Any ideas what can I use to get rid of it?