A simple, cheap and effective short term solution is to use regular unflavored oatmeal available in any grocery. Run it through a blender to make it extra fine, and use a cup of oatmeal to about a gallon of warm water (you can experiment to see what works for your pet, and smaller pets could use less oatmeal and water.)
Rinse your pet with the solution, let it stand for 10 minutes and towel off.
This can be repeated as often as needed..