I'm planning to cover up an open coil humbucker, with a cover that has no holes exposing the slugs, that looks something like this (it's simply easier to keep clean):

I watched this video on the subject, as far as I understand the process explained here is:

• Create a barrier between the plastic top/slugs and the cover using wax
• Insert the pickup
• Solder on both sides of the back
• Functionally we are done

What I don't understand, is what are we trying to achieve with the wax?

• Are we trying to prevent conductance between the cover and the slugs in the pickup?
• Or are we trying to make sure the pickup doesn't rattle in the cover (budget wax potting)?

Thanks for any info!