The way we cut our sails was on a table with a ruler at the bottom and a large carpenters square. That way we could relatively quickly plot the XY coordinates and draw a relatively fair line through the dots.
Getting some templates will be faster I think, but you still need to mark the seamlines for the overlaps/broadseaming, hemming etc. Any shop with access to a plotter can do this for you. Or talk with a local sailmaker and have him sell you the cloth already marked and cut?