It's just like cleaning a tent or something similar.
For my vert, it was simple. I've done it a few times and no problems with mould over winter etc. Bird sh*t just sucks regardless.
Tools:
Brushes, soft and a couple of sizes. Large and small like a tooth brush.
Foaming carpet cleaner; you can use any product but here is an example - https://www.supercheapauto.co.nz/p/sca-carpet-and-upholstery-foaming-cleaner---400g/393394.html?cgid=SCN010103
Spray on protection; as above, you can use any product but here is an example - https://www.supercheapauto.co.nz/p/sca-fabric-protector---400g/414727.html?cgid=SCN010103
A bunch of microfiber cloth
Elbow Grease
Bucket full of warm water
I would recommend a nice sunny day to do this. It requires a few hours due to steps.
How to:
1. Clean the roof.
Spray it down with water first with cold water, just get crap off it.
Once it is clean, spray foaming cleaner on a section, start scrubbing with a brush, use a brush that suits the size of what you are working with.... Note: You should test your brushes first to make sure they aint too harsh and do damage to your cloth.
Make sure you are rinsing the roof off before moving to another part of the roof.
Once you are done here, rinse it all off with warm water to help it dry faster.
2. Leave to dry, have a beer or jam out with a hair dryer.
Use micro fibre clothes to dry off the corners and rubbers. May need to dry more.
4. Once dry. Move car in a roofed and non windy area, like a garage or a car port.
5. Spray protective spray, this may need several coats, read product instructions.
You're done. Just leave it to cure, should be good for another 3/6 months depending on exposure to weather really.
Or you could just lazy it out... water blast the crap out of it -> dry -> spray fabric protection -> walk away...