Be careful with the food colouring..... even if you seal it clear spray.. if a kid chews on it, the food colour will end up on faces and hands!
Watered down acrylics work for me too.... just wish they wouldn't raise the grain so bad.
As for clear spray, we don't have as many choices here as you folks in the US have. One I used a lot was Estapol, but the forever clogging up nozzles made that a very expensive spray to use. After contacting them about it they did give me some free cans, but also told me they do not fill them themselves and could not guarantee I wouldn't keep having the problem.... they went as far as telling me I might consider buying a different brand.
I've tried everything, always making sure I turn them upside down and spray until clear ( then I ran out of propellant before the can was empty) and even stored them upside down...
Does anyone have any other ideas?
Juvy