There are no problems with water...
...the best part its cheap (free if you have a tank and a tiled roof) :)
A good douse in contact cleaner will move the water residue, never had an issue with rust or anything like that.
It gets superb results, I always gain something out of a motor, generally a minimum of 500 RPM (rear wheels), best I have got out of a stock Scaley motor is 12200RPM at the rear wheels, an average motor out of the box is about 10500-10800RPM.
That makes for a large advantage in competition.
The really cool thing is the motor does its break-in stress free, no heat, no load, bedding a motor in on the track will never get the same results.
Phil Wicks! He is a "Smokey" from way back, Harry and Phil have showed me a lot of most excellent stuff over the years...
...Phil is that far ahead of the blokes he races with it isn't funny (well it is, but....) :D