Doesn't work mate, they just go all pasty. I've done it with GLM powders, liver powders etc. It's the heat that makes them sweat. Only cooling will prevent it.
I'll generally give the spot one big hit for the night ahead (at least a gallon plus whatever else I'm using with them) but that's because the lower stock waters I fish do not tend to respond well to the constant disturbance of the little/often approach.
When the fishing is tough there is no better method imo. I've had sessions where I've been forced to top up in the night such is their effectiveness. When they're bang on it you can get through gallons and gallons.