Hi, thanks for your interest in Halfords and our Autoglym products. For best results you should spray onto the surface and then use a suitable brush to brush over the surface to agitate contaminates (A paintbrush is Ideal). A hose can then be used to wash the product off. Only use on cool surfaces and do not allow the product to dry. You should avoid directing water at air intakes or elctrical/electonic components. Protect vulnerable items with plastic film. Hope this Helps. Thank You