Aye, I lay the sails
on grass and scrub with soap and water
, then rinse and repeat.
Not sure about rust remover, usually that is acid and could hurt the fabric
Try mild stuff, but not the Must For Rust available at Home Depot. (I use it for SS on the boat, but not on no sails)
If the sails have been stored for years onboard and full of mildew, try a mixture of vinegar and citric acid. (Squeeze lime and lemon in the vinegar/water mix)
Would check with the manufacturer first, but should be ok..,Maybe.
There is companies specializing in cleaning
sails, here in Florida
, Second Wind
Sails, but they charge a few hundred $$..