The gunge won't reach the paper filter itself, only completely block the breather pipe. What it might do though, is to muck up the membrane type flap inside the air filter casing. So once you've cleaned the pipe, open the casing and remove the paper air filter. You will then be able to see the membrane flap (not correct technical name) which is easy to check and clean.
The Haynes manual will have a full description of how to do this. Borrow one from your local library if you don't want to buy one.