i ordered and received a Guardian Silicone Lens Extra Heavy Duty Gasket from InYoPools.  Does the gasket require any grease on it to help it seal?  After installing the gasket when I tried to put the light fixture back in the niche, the fixture started bubbling, so I took it back out.  

 I did not see any instructions with the gasket and the DIY video on this site did not say anything about grease.

Thanks for any insight.