Sailcare is the only thing I have dealt with. Not sure what they use, but boy they do nice work. I am not advertising, but I know they did a helluva job on some 25+ year old sails we had. Got most of the rust off too.
As for doing it yourself. I suppose a non-bleaching detergent will get marginal results at least. as for the rust? I dunno, maybe oxy? With what sails cost if you mess it up, I dunno I'd want to take the chance.