Renovo roof cleaning system is 3 products - shampoo, colourant (if required) and water proofer. The shampoo is applied with a stiff sponge, left to soak, you then hose it off - you'll be surprised how long it takes before there's no suds in the water coming off!
The colourant is thinner than water, so you need to mask off bodywork and drainage channels and use it carefully. If any gets on the bodywork wipe it off immediately with a soft cloth, it's a pig to get off once it's dry. Also do not fold the hood for at least 24 hours after applying or you'll get white crease marks.
The waterproofer is easy to apply, again you have to leave it to dry.
If the hood does not need recolouring, a cheaper option for waterproofing is stuff from a camping shop for doing tents - Fabsil Gold.
I used all of the above on my 968 cab, all 3 when I first bought it (hence the "ask me how I know" comments!) and it came up like new and lasted that way (although reproofed every couple of years) for about 5-6 years!
I believe the Autoglym stuff is similar, although I've not used it. Renovo and Autoglym are the 2 brands that invariably get good reports when your question has baan asked on the 4 car forums I frequent.
