We used to have some stuff in the Air Force called "F-4 tape" which
worked great for this sort of thing. It's kind of like a putty tape, in
rolls with plastic separating each layer of the tape.

a.k.a. 3M Scotch 70 Silicone Fusible Backshell Tape, apparently.

Sounds like good stuff... sort of the high-tech, stable-silicone big
brother of the less-expensive self-amalgamating rubber electrical
tape. Not cheap, though... list price for a 1" by 30' roll is on the
order of $30 in quantity, over $38 in onesies. Ouch.


I'll just stick to Coax-Seal (tm)
http://www.coaxseal.com/