Michael -

A rubber bung with an airlock should make a good seal if it is
inserted firmly. You don't need layers of plastic.

At two years, though, I have to wonder why you don't just bottle the
wine and be done? With airlocks, you need to check them regularly, to
make sure they don't run dry. If you use decent-quality corks, and
store the bottles on their sides, you really shouldn't need to worry
about the wine once it is in the bottle.

Doug