Not hard to do
Reefing the sail on an O'DAY 12 was possible using a few extra lines. I have to admit that although I am somewhat familiar with the 12, I'm answering based on the pictures that I have and my basic knowledge of how to reef using jiffy-reefing. The 12 had "Jiffy-Reefing" standard, to reef the sail you would first lower the sail enough to bring the grommet for the reef tack (grommet in leading edge of sail, about 24" up from boom) down to the boom and tie to the boom with a short line (maybe tie to normal tack grommet?). Now untie/unhook the outhaul from the normal clew grommet, and attach to the reef clew grommet, you will need to loosen the outhaul to do this, then tighten the outhaul a bit. There should be 2 additional reefpoint grommets located between the tack and clew of the reef, gather up the "extra" sail material and use a short (18" +/-) piece of light line through each reefpoint to hold the sail in place, these should be tied around the gathered sail material but not the boom.It is a lot easier to do than to explain!