I accidentally bought push back wire with shielded exterior. I was going to use copper tape lining to reduce hum though. I can't just use this combination together as is or it will ground loop everywhere. Is it fine to just buy some shrink tube to put around these wires to solve the problem rather than buy new wire?

Also I was wondering if I need to insulate the body of metallized film capacitors when the cavity is copper lined. Or is the plastic shell it has good enough and only the leads need insulation.

Thanks. I would appreciate your time and any advice. I can't find an answer online.
If interested to know this is my first time rewiring a guitar. It is an early nineties Vantage superstrat with a layered through neck.

You can use both. It doeant really matter if the wire shield touches the foil, but if you want to be anal about it then you could insulate the wire with heat-shrink tubing.

And the body of the cap is already insulated.