I use 30 minute epoxy that I buy from the Hobby store (Great Planes).... mix a little bit of it with the activator and brush it on... it wont affect plastics like the nail polish will. Just make sure that you have a bunch of disposable brushes... because they are ruined after you use them. I usually wait until I have enough jigs ready to make it worth while.
On small jigs I just use Sally Hansens but on spinnerbait heads or large bass jigs I use epoxy. I over pay I know but I use the WTP 3D eyes and I have used them without a seal coat for an entire day fishing and the eyes didn't come off. The eyes are a lot more expensive but the adhesive they use is excellent so I'm confident in just using the Sally Hansens on the smaller heads.
I have some CSI Seal Coat I put over them. Seems to stick pretty well. I keep it in one of those jars with a built-in bodkin. I use the bodkin to dab a drop over the eye and spread it around then hang them to dry.