Resin is a tricky substance to work with, but if you take the time to learn a bit about what you are doing it can be simpler than you might have ever imagined. A hermetic coaxial connector is often used to help create a passage way that is fully sealed into a resin tank while resin is curing. You can create your own hermetic coaxial connector if you use the parts that are already present.
Taking a nut for instance off of the tank that you want to add the connection to can offer you an area that you can access. First, you should remove the nut then create the opening. You then put your connectors into the opening that you have created in the nut. A plastic laser cut cover is a fantastic way to seal the connection to help keep it in place and to ensure that the connection is fully sealed.
Resin can then be poured to create the hermetic seal and also allows you to make sure the seal is tight and that no air or gas is going to be able to escape around the edges of the seal. This type of connector is easy enough to make if you have the tools and the knowledge to do it.