Renovo do the full 3 part kit, which I used on the dark blue hood of my 968 cab just after I got it. Stage 1, scrub the shampoo into the soft top with a small scrubbing brush, leave a while then rinse off - hose and quite some time until the suds stop. Let the roof dry comletely. Stage 2, mask up so the colourant does not go where it should not, but have a damp cloth handy as it's thinner than water, easy to remove when wet but a PITA when dry (guess how I know). Follow the instructions to re-colour the roof, especially "do not fold the roof for at least 24 hours after application" or you will get white crease marks (again, guess how I know!!). Once roof is completely dry, stage 3, apply water proofer and allow to dry. Bit long winded but lasts well, in the 6 years after I did it I re-proofed the roof with Renovo until it ran out then Fabsil Gold which I happened to have, and it still looked good.
Been a number of threads on this subject, Renovo and Autoglym stuff always get good reports, as do Milton, Johnsons baby shampoo and Fabsil Gold.