Sail Care folks processed several sails
for me about 20 years ago. Company ownership
has since passed to employees who did the work for me back then. The sails were terribly dirty/stained and they came back like new. Minor stitchining was also performed. The resination process returned considerable body to the sails and I was satisfied with the end result.
Since then I've had new sails cut, but most of the resinated sails remain usable (unfortunately, I haven't been sailing for too many years). Of course, the condition of your sails is integral to the degree of success with this process. They can't turn rags into new sails.
Feel your way with them on the phone
. Send one sail and see how it goes, which worked for me.