Refer Refer AD/PT6A/28.
http://www.casa.gov.au/scripts/nc.dl...e=PT6A-028.pdf
We try and cool ours for 90 mins prior to washing. Pointing it into wind helps. Other than that not aware of any methods to expedite the cooling process.
The maintenance manual on a PT6-114A calls for the engine to be brought up to 80% Ng for 1 minute to dry it. Exercise the heater as well as it often collects small amounts of water that will eventually lead to corrosion. Particularly important following a performance wash.
Drying run not really necessary if the aircraft is going flying following the wash.
D.