Hi Cat Kit, I was in the same boat as you a month ago and my roof needed cleaning/re-sealing.
I bought the auto-glym cabriolet cleaning kit for about £18. It contains a shampoo and a re-sealer. There are a few different brands which sell similar kits; turtle wax to name one. As far as I know they are all pretty much the same animal - shampoo & sealer. You'd be better off doing it in the morning when there is a clear weather forecast for the next 24-48 hours if you only have a driveway like myself, if you have a garage and can keep the roof dry when you have finished just 3 hours of clear sky required.
I bit the bullett and just followed the instructions... worked well for me, water beads in the dew every morning and water runs straight off when I wash it! I think it took me about an hour and a half, but give yourself 2 hours and make sure there is no hose-pipe ban active in your area...
Firstly you hoover the roof - I thought this a bit odd but it removes fluff and dirt so it does not get clogged in the roof material when shampooed (I think?). I used the hand-held attachment on mine - took about 5-10 mins.
Then you used your hose to generate a fine mist over the room to dampen it.
Then use the shampoo and cover the entire roof with a reasonable about (from memory I think I used 1/3rd to 1/2 of the 500ml bottle). Give it a minute of two to sink into the fabric. (Took maybe 5 mins?)
Then use the sponge to "aggetate" the shampoo. I used a circular motion where possible until the shampoo foamed slightly all over the roof. I worked from one side to the other and then back again to make sure it was washed thoroughly. (Took maybe 30mins?)
When you are done with the shampooing you will need to rinse the roof. Again use the hose for this and be sure to rinse ALL of the shampoo from the roof material. This takes a while as the shampoo gets into the fabric and creates foam... (Took maybe another 30mins?)
When there are no more suds coming from the roof fabric the roof has been 'cleaned'. Now all is left is for you to re-seal it. For this the roof needs to be DAMP. At this point it will be sodden from the thorough rinsing you have just given it. I used a towel (dark colour just in case) and laid it over the sections of the roof (took about 8 goes with a medium sized towel). Then you use the sealer included in the kit and spray the whole roof. If you get any on the chrome trip and windows just wipe it off. I think I used about 1/2 the spary when I did mine. (Takes maybe 15-20mins?).
You must be sure to allow the sealer to sink in the to allow the roof to dry fully before exposing to moisture according to the instructions. Then when this has soaked in and been left to dry overnight you are done!
I've basically reitterated the instructions with the kit, however I hope this is of some use. I've still got enough of the kit left for another wash/re-seal so for under £10 and a few hours work you've got a clean and 'waterproof' roof again - a bargain in my eyes. Personally I'm going to clean/seal mine every 6 months or so but I have been told every 12 months or 'when water does not bead' is acceptable.
Good luck with the cleaning!
