I have heard good thinkgs about the Renovo stuff.
I have only used the Autoglym 2 step method. It is easy to apply and really does a great job - water beads really well.
The first step is the cleaner which is sprayed on and then you use the sponge that comes in the kit to aggitate the cleaner and remove bad mark' s/ stains.
You then wash this off, either with a hose or watering can. I would not use a jet washer unless it can be on a really low pressure.
The second part is the sealer, which is sprayed on. Be careful not to get any on the windows or body work as it will set quite hard (like tree sap) quite quickly. If you do get any on the glass or bodywork, wash it off straight away.
I purchased this from Halfrauds when they had the 2 for 3 cleaning offer on which I believe is finished now. It cost about £16.00 I think.