I started with the caravan roof as it is the hardest to clean with baked on grime. As instructed I hosed down the roof. Put 30mil (this bottle will last for ages) in a bucket with warm water. I sponged the roof and the grime seemed to come off quite easily. I left the roof as instructed for ten minutes then hosed off. It really did come clean and worked a treat. Thoroughly recommend this product. Cant remember the price, I think, $19-95. Worth it as I will get many washes out of it.