Here’s a link to a thread from 2005, in which we discussed the topic of furled sails at some length. My own personal approach to the subject is in the post under my name for Jan. 14, 2005, a few posts down from the beginning.
Here’s another link to an article on the Model Ship World site that covers this topic. The implication seems to be that I wrote it, but several folks contributed to it. Scroll down to "Making and Forming Sails for Your Model " and click. Much of the text is lifted from the FSM Forum post referred to above. There are also photos of a couple of my models.
http://modelshipworldforum.com/ship-model-rigging-and-sails.php
Two caveats. One - don’t bother clicking on the links that supposedly take you to more photos. That site no longer exists. Two - the latest issue of Model Railroader contains the deeply distressing news that Testor is taking both PolyScale and Floquil paint lines off the market. I haven’t used this sailmaking technique in several years, and I’ve never tried it with any brand other than PolyScale. I suspect the acrylic “craft paints” sold in arts and crafts stores would work just as well for this purpose, but I don’t know that for a fact.
Hope at least some of this helps a little.