flat5

I would not advise the foil. It would be an intermitant connection at best.

The shields will solder well if everything is clean and already "tinned".
If they don't reach each other just add another piece of wire.

The easiest way to make the cord strong is to tie a slip knot around the splice. Is that clear?

Also, Google "good soldering practices".

Use a reasonable quality iron of the correct wattage for the job.
 Only use "electronic" resin cored solder of fine gauge.
 Make sure all surfaces to be soldered are "bright, shiny" and thoroughly clean.
 If a mechanical joint, make sure it can "stand alone" before soldering.
 Make sure the solder tip is clean, shiny and properly "wetted".
 Remember the soldering iron tip is only to heat up the surfaces to be soldered.
 Apply the resin cored solder to the heated "job", not to the soldering iron tip.
 Remember to visually inspect ALL of your soldered joints, preferably with magnifying glasses.
 Consider using your multimeter to provide an "electrical continuity" check between various parts of the circuit.