I have been using the same bottle of Jerrow's for YEARS. It is supposed to be non-drying so shouldn't harden up too much. When it is right it should have a consistency like mayonnaise, maybe a touch thinner. I will occasionally give mine a stir just to make sure it is mixed well but it doesn't seem to separate all that much if you're using it on a regular basis. If yours is thicker than the above consistency or is chunky, toss it and get a new one. DES/TSD is right on about using a thin application and taking your time.
