Alcohol is good,I've used both surgical alcohol & the stuff we call Methylated spirits in Australia.
The "Metho" does leave a white deposit,but it is fairly harmless,& if you use paper towels, Kimwipes or similar,you can wipe it off as you go.
There is a product that RS Components sell in Aust,& probably the UK that comes in a pressure can & looks like
shaving cream. This is very effective,we used to spray it on,wait about 10 minutes & wash it off with water.
We started off with Distilled Water,but after a while,we went with plain tap water with less critical circuits.
We would then dry with compressed air, followed by a heat gun.It gets pretty hot in the summer here,so just leaving them out in the sun is another option.
We did not experience any increase in failure rate using this method.
Obviously,everybody wants to send their boards out in pristine condition,but you can go overboard with worry about "contamination". If you look at boards in service in industry,they will work OK,even with the most horrendous contamination due to the enviroment in which they operate.
Even in fairly benign environments such as TV Studios,there was an amazing amount of crud on the boards.
One warning about water use,if you have things like IF cans,etc,these things are only shielded for RF,they are not watertight.
Most of the PCBs you will encounter will not use such devices,although maybe getting water & crud under large ICs might not be good.
VK6ZGO