Finish brewing my first batch last night… I also had to drill a hole in my lid. What I
did was I went down to my local hardware store and picked up a “5/8 wire
grommet”. In my opinion it is the best option, when you put the air lock through, it
will fit very snug and will be air tight. If you can’t find one I would use a #2
stopper… I don’t know what size stopper you have but anything around a #7
would be too big and look ugly but I guess it would do the job. And yes sanitize
everything, bucket lid, stopper/grommet, air lock… take it all apart and soak it,
including the rubber gasket on your lid (if you have one).