Certain stains need to be addressed as soon as possible specifically Bird Poop. It’s very acidic and will discolor or dissolve the fabric if left. I live on the edge of a bird sanctuary, so I know this well. I use my hose with some force to knock off as much as possible. If there is anything left, I use a mild dishwash detergent, spray liberally then hose off again, in some cases I will brush the spot lightly.
More detailed cleaning and maintenance information can be found towards the end of the manual. Here is a link to new manual: https://www.dropbox.com/s/dj8eso49qe7lufs/SG%20Manual%202019%20-English%2016.11.2018.pdf?dl=0