Tom,

For what it's worth, I haven't used the black stuff in years.   A nasty mess 
to get off later.  This is one reason some guys put down  a layer of black 
electrical tape first.    At some later time, you get off most of the black 
goo and  then cut or peel the electrical tape off and your connectors are 
still bright and shiney, not all gooped up.    Some guys put the first layer 
of tape with the sticky side up to make it even easier to get off.

 I prefer cold fusion or silicone tape that can be gotten at Home Depot or 
any electrical supply.  HD has them by Gardner
Bender and 3M.   About 3 bucks a roll.   Cut a little less then you need. 
Peel off and throw away the mylar backing film    Stretch the piece 
lengthwise and it will  get about 50 percent longer.  Stretching also 
activates it.   Wrap it overlapping a bit and  squeezing  with your hand to 
smush it all together.     Final wrap  with a layer or 2 of good  outdoor 
type electrical tape like Scotch Super 88, another 3 bucks a roll at HD. 
Good tight seal and  easy to get off later with no mess  left behind.

Whenever using tape, the final  wrap should  be done from bottom to top and 
the layers will overlap like the shingles on a roof and water won't  try to 
get under the tape.

73 Steve KW3A