Is it necessary to put a little plastic piece over the plug ends when you have finished soldering a new plug onto the cable? or can you wrap electrical tape around that then screw the barrel on? Also when you are soldering your ground to the chassis piece do you drop some solder on to it first before you solder the wire to it? I saw on a Y/tube video some person was applying a liquid to the wire ends before tinning them. Would that be liquid flux? Thanks.