I used MG 832 epoxy Black Epoxy

Be aware that whatever you potting you need to seal all gaps to make sure potting compound gets only where you need it.
For example this MG epoxy seems thick but it will get into smallest voids and leak if not properly secured.

Also this one is permanent, hard stuff, impossible to remove without braking whatever was potted.

You may look into some urethane based potting compounds, these are soft and flexible.

Stay away from stuff that is not meant for potting. Some epoxies shrink or expand too much when curing. It may cause electronic components to dislocate and break circuit.