Crotons are not particularly sensitive to any standard liquid dish soap. Soap is more effective than alcohol in treating mites because it spreads more readily. The key is to spray the soap enough so that it washes over all leaf and stem surfaces and makes contact with every last mite. If your plant is small enough, invert the plant and swirl it around in a sink filled with soapy water. That ensures complete coverage and is easier and less messy than spraying.
