I think what he means is that you should use differing colored wire for eac direction.
+ would be blue
- would be red
if your looking to use the amp ( i cant be assed with it) then things are gonna get tricky.
my advice is just skip the whole amp method and go direct.
some people wont like that , but its easier.
al i can say is that when your using the tape , id say use double sided and sticked the amp(if you go with it) to the inside part of the case.
good luck.