Washing out a gearbox

[LongBaz463BHP]

Got the gearbox out of the car to inspect the stripped 5th gear, which was totally mashed. What is the best way and what solution would be best to use to clean it out.
Thanks
Barrie

[LongBaz463BHP]

Thanks for the replies, do these options also apply to the gears and bearings etc.
Barrie