I've used that plastic dip type stuff before, it's good for basic insulation and providing a rubber like coating but not very durable as as potting compound, any general purpose epoxy should work fine and be tough as nails, go for a long set epoxy if you can as generally speaking the longer the epoxy set time is the less brittle hence stonger it will be once it sets. Epoxy putties might work too and could be formed into a more pleasing final shape but I'd be a little wary of how conductive they might be. Liquid epoxy for the protection and then epoxy putting for the final shape would probably work well, the putty I have takes well to sanding and shaping after it sets, and should take paint with a primer if you want it to look really pretty.