Heat shrink is awesome. Only discovered it recently; having always used insulation tape in the past. I'll never go back!
Only one addition to what Viney says - make sure you are soldering onto clean wire i.e fresh wire that you have removed the insulation from.
And gas powered soldering irons FTW
(there are a few youtube vids kicking about, though they are pretty annoying as Americans have this stupid way of pronouncing "soldering".)