if you are doing a full clean up job get yourself one of these:-
http://www.ebay.co.uk/itm/Digital-Ul...item1e9003cfe8
A quick clean in soapy water to get the worst off then into the USC with hot water and a few drops of fairy.
When cleaning gearboxes and internals change the water for some engine degreaser, then another cycle or 2 with hot water and washing up liquid.